25.0.0: CURRENT:
Electric current is the time rate of flow of electric charge along a conductor. Current is produced when an electric charge flow from one point to another in a circuit. The s.i .unit of current is ampere and the symbol is A. For current, I is used.
FORMULA FOR CALCULATING CURRENT:
Current I = Charge measured in Coulomb / time measured in seconds.
Current = charge / time
APPLICATION OF FORMULA TO SOLVE PROBLEMS:
EXAMPLES:
*Calculate the current generated when 250 coulomb of charge flow in a circuit for 3½ minutes.
SOLUTION:
Data given in the question:
Charge = 250 Coulomb, time = 3½ minutes = 3½ * 60 seconds = 10/2 * 60 seconds = 10 * 30 seconds
Time = 300 seconds.
Formula: Current I = charge / time
Substitution: Current I = 250 Coulomb / 300 seconds
Current I = 0.833 ampere
*Given that the current that is generated in a circuit for 5½ minutes when a given quantity of electric charge flows through a conductor is 1.25 A, determine the charge.
SOLUTION:
Data given in the question:
Current I = 1.25 ampere, time t = 5½ minutes = 5½ * 60 seconds = 11/2 * 60 seconds = 11 * 30 seconds
Time = 330 seconds.
Formula: current I = Charge / time
Substitution: 1.25 = charge / 330
Make charge the subject of the formula: charge = 1.25 * 330
Charge Q = 412.5 Coulomb
*Calculate the time for which 3000 Coulomb of charge will generate 2.25 A of current in a circuit.
SOLUTION:
Data given in the question:
Charge Q = 3000 Coulomb, current I = 2.25 Amperes
Formula: current I = charge / time
Substitution: 2.25 = 3000 / time
Make time the subject of formula : time = 3000 / 2.25. Time = 1333.33 seconds
AMPERE:
Ampere can be defined as the flow of one Coulomb of charge in one second. It is the unit of current.
COULOMB:
Coulomb is defined as the quantity of electricity that flow through a conductor in one second when the current through the conductor is one ampere. Coulomb is the unit of charge.
AMMETER:
Ammeter is an instrument that is used for measuring current. Ammeters that can detect and measure small current are called milliameters. Galvanometers are ammeters that can detect and measure very small current.
SENSITIVITY OF AMMETER:
An ammeter is said to be sensitive if it can detect and measure a very small current or detect and measure current no matter how small the current may be.
CONNECTION OF AMMETER:
Ammeters are connected in series in a circuit so that the current the ammeters are to measure will flow through the ammeter themselves.
ACCURACY OF AMMETERS:
Ammeters are said to be accurate if it can detect and measure the exact amount of current that flows through it or if the current it detect and measure is very close to the value of current that flows through it.
ELECTRIC CIRCUIT:
Electric circuit is the Path through which electric current flows in a circuit. It consist of the source of electric energy connected through a conductor to a load and a switch.
TYPES OF ELECTRIC CIRCUITS:
Closed circuit:
A closed circuit is a circuit that is in the on position. In a closed circuit, the current flows through an external resistor. The resistor can be a bulb or any alliance connected in the part of the current.
DIAGRAM OF CLOSED CIRCUIT:
OPEN CIRCUIT:
An open circuit is a circuit that is in the off position. In an open circuit, the battery maintain no current in an external resistor and the bulb.
DIAGRAM OF OPEN CIRCUIT:
Short circuit:
A short circuit is a closed circuit that has no load connected to it.
DIAGRAM OF A SHORT CIRCUIT:
POTENTIAL DIFFERENCE P.D:
For electric current to flow in a circuit, there must be a pressure difference between the two points in the electric field. This pressure difference is the potential difference.
DEFINITION OF POTENTIAL DIFFERENCE:
The potential difference between any two points in an electric field is the work that is done in moving a positive charge of one Coulomb from one point to another in an electric field.
It can also be defined as the electrical pressure difference between the two points in an electric field. Potential difference is measured in volt, (V).
ELECTROMOTIVE FORCE EMF:
Electromotive force is the total work done in driving one coulomb of electric charge round a circuit. Of can also be defined as the total energy per Coulomb obtained from a cell. The unit of emf is volt, V. Emf can also be defined as joule per Coulomb.
FORMULA FOR CALCULATING EMF:
Electromotive force emf ( E ) = work done in joule / charge in Coulomb.
Recall that Current I = Charge Q / time t. charge q = current I * time t ( Q = I * t )
We can bring in this formula into the formula of electromotive force. Therefore,
Electromotive force = work done / ( current* time )
If emf is measured in volt, work in joule and charge in Coulomb, then
Volt = joule / Coulomb
APPLICATION OF FORMULA IN SOLVING PROBLEMS:
EXAMPLES:
*Calculate the work done by a cell of emf 12.5 volt if a charge of 250 Coulomb is maintained in the circuit.
SOLUTION:
Data given in the question:
Emf = 12.5 Volt, charge = 250 Coulomb, work = ?
Formula: emf = work ( w ) / charge( q )
Substitution: 12.5 = work / 250
Make work the subject of the formula: work = 12.5 * 250. work = 3125 joules.
*320 joules of work is done in electrical circuit. If the charge that flow in the circuit is 1250 Coulombs, determine the electromotive force of the cell in the circuit.
SOLUTION:
Data given in the question:
Work done = 250 Joules, Charge = 1200 Coulombs, electromotive force = ?
Formula: electromotive force = work done / charge
Substitution: emf = 250 / 1200 . emf = 0.208 volt.
DIFFERENCE BETWEEN EMF AND P.D:
Electromotive force is the potential difference between the terminal of a cell when it is not delivering any current in an external circuit or when they cell is in an open circuit.
While potential difference two points is the work done In moving one coulomb of electricity from one point to the other. The unit of potential difference is volt.
PRODUCTION OF ELECTRIC CURRENT:
Electric current can be produced from the following:
Chemical energy
Heat energy,
Mechanical energy
Solar energy
1..PRODUCTION OF ELECTRICITY FROM CHEMICAL ENERGY:
Electricity is produced from chemical energy through the use of cells.
CELL:
A cell is a chemical pack that produced is a chemical pack that produces current due to irreversible chemical reagle.
COMPONENTS OF A CELL:
A cell consist of positive anode and negative cathode that are separated by solution of various acid or salts.
ELECTRODES:
Electrodes are the positive and negative terminals of a cell. Current leaves the cell through the positive electrode and enters the cell through the negative electrode.
TYPES OF ELECTRODES:
There are two types of electrodes. They are :
The Anode
The Cathode
THE ANODE:
Anode the positive electrode / terminal of the cell. Current leaves the cell through the anode.
THE CATHODE:
The cathode is the negative terminal of the cell. Current enters the cell through the cathode.
ELECTROLYTE:
Electrolyte is the chemical composition of the cell in which the electrodes are immersed. The electrolyte is in a molten form so the that the electrons would be able to move about and constitute current.
SIMPLE CELL:
A simple cell consist of a copper rod as the positive anode and a zinc plate as the negative cathode immersed in a container that is filled with dilute sulphuric acid ( tetraoxosulphate (vi) acid ).
DIAGRAM OF A SIMPLE CELL:
WORKING PRINCIPLE OF A SIMPLE CELL:
When the switch is closed so that the copper and the zinc plates are connected together, the zinc slowly dissolves in the acid by chemical reaction. Electrons and bubbles of hydrogen gas are produced. The electrons flow through the wires from the zinc to the copper and produce current while the bubbles of hydrogen gas are formed on the copper anode of the cell.
CONVECTIONAL FLOW OF CURRENT:
In a cell, current flow from the positive anode to the negative cathode while electrons flow from the negative cathode to the positive anode. This opposite movement of current and electrons icps called convectional flow.
DEFECTS OF SIMPLE CELL:
Simple cell can only supply current for a short time due to its defects that is discussed below:
POLARIZATION:
Polarization defect is due to the formation of hydrogen gas bubbles on the copper anode of the cell. The hydrogen gas bubbles cover the copper anode and set up a back emf which oppose the forward emf of the cell. The back emf gradually reduces the current in the external circuit and eventually stop the chemical action of the cell which in turn stop the cell from working.
PREVENTION OF LOCAL ACTION:
Polarization defect can be prevented by the addition of chemicals called depolarizers such as manganese dioxide and potassium dichromate to the electrolyte.
FUNCTION Or ACTION OF DEPOLARIZERS:
The depolarizers oxidizes the hydrogen gas bubbles to form water.
LOCAL ACTION:
Local action is the wearing away of the zinc plate into the acid. Local action is due to the present of impurities such as iron and carbon in the zinc. The impurities set up tiny cells around the zinc surface and produce hydrogen bubbles on the zinc surface.
PREVENTION OF LOCAL ACTION:
Local action defect can be prevented by the process of amalgamation. Amalgamation is the rubbing of the zinc plate with mercury. The mercury prevents the impurities from touching or coming in contact with the acid and therefore prevent local action.
2.. PRODUCTION OF ELECTRICITY FROM HEAT ENERGY ( THERMOELECTRIC EFFECT ):
Electricity can be produced from heat using a thermocouple. Electricity is when there is a difference in temperature between the hot junction and cold junction of the thermocouple.
THERMOCOUPLE:
A thermocouple consist of a copper and iron wires at one end and the free ends are connected to a galvanometer.
DIAGRAM OF THERMOCOUPLE:
WORKING PRINCIPLE OF THERMOCOUPLE:
A thermocouple has a cold junction and hot junction. When the hot junction is immersed in hot water so that there is a difference in temperature between the hot junction and the cold junction, current flow in the wire of the thermocouple. The current is detected and measured be a galvanometer connected to the free ends of the two different wires. The higher the difference in temperature between the hot junction and the cold junction, the larger the current produced by the thermocouple.
THERMOELECTRICITY AND THERMOELECTRIC EFFECT:
Thermoelectricity is the electricity that is produced by a thermocouple while the effect that produced the current is called thermoelectric effect.
3..PRODUCTION OF ELECTRICITY FROM MECHANICAL ENERGY:
Electricity is produced from mechanical energy when a coil of insulated wire moves and cut across the magnetic field of a magnet. Current is induced in the coil and is tapped out through the split rings/ commutator and carbon brushes to which the ends of the coils are connected. The device is called generator or dynamo
AC GENERATOR:
An ac generator is a device that convert mechanical energy into electrical energy when a coil move and cut across the magnetic field of a magnet.
CONSTRUCTION OF AC GENERATOR:
An AC generator consist of a coil placed in the magnetic field of a north and south poles of a magnet. The ends of the coil are connected to two slip rings. The rings are connected to two carbon brushes. Current is tapped out through the two carbon brushes by wires connected to them.
4.. PRODUCTION OF ELECTRICITY FROM SOLAR ENERGY:
Electricity can be produced from solar energy. The device that is used is called photoelectric cell or photo cell.
PHOTO CELL:
A photo cell is a device that convert solar energy of the sun into electrical energy or electricity. It consist of a photosensitive surface metal such as potassium and alkaline metal that emits electrons when light incident on it.
DIAGRAM OF PHOTO CELL:
WORKING PRINCIPLE OF PHOTO CELL:
A photo cell consists of a light sensitive metal surface. When solar ( light ) energy from the sun incident on the metal surface, the metal surface emits electrons by photoelectric effect. The emitted electrons then flow in the circuit and constitute the current which is detected and measured by a galvanometer connected in the circuit.
THE ELECTRIC CIRCUIT:
I have discussed electric circuit before now. Here, I will center on some components that are commonly found in electric circuit.
As I defined earlier, electric circuit is that which electric current flows in a circuit. A circuit usually consist of cell which is the source of electric energy, a switch, an ammeter which measure the current that flow in the circuit, a voltmeter which measure the potential difference across a component, a resistor which is the load, a rheostat which is used to adjust the
AMMETER:
An ammeter is used to measure current that flow in a circuit. It has a small resistance. It is connected in series in the circuit so that the current it will measure should flow through it.
CIRCUIT CONNECTION DIAGRAM:
VOLTMETER:
A voltmeter is used to measure the voltage or potential difference across a component in a circuit. It has a large resistance. It is connected in parallel across the component whose voltage drop is to be determined. It takes in negligible amount of current.
CIRCUIT CONNECTION DIAGRAM:
RESISTOR:
A resistor is an electrical component that oppose the flow of electric current through itself.
STANDARD RESISTOR:
A standard resistor is a resistor whose resistance is known and fixed. Standard resistor is usually in the form of length of resistance wire or a piece of carbon.
Constantan or manganin are used for making standard resistors because their resistances is are little affected by temperature change.
VARIABLE RESISTOR OR POTENTIOMETER:
A variable resistor is a resistor whose resistance is not fixed. It is a resistor that has different values of resistance. The resistance of a variable resistor can be changed to any desired value. Rheostat is an example of variable resistor.
RESISTANCE:
Resistance is the opposition that a resistor offered to the flow of electric current through itself. The unit of resistance is ohm.
DEFINITION OF OHM:
Ohm is defined as the resistance of a conductor when a potential difference or a voltage of one volt is applied across the conductor causes a current of one ampere to flow through the conductor. The symbol used to represent ohm is ...
NON OHMIC MATERIALS:
Non ohmic materials or conductors are those materials or conductors that do not obey ohms law. They are materials in which the current that flow through them do not increased as the voltage connected across them is increased.
EXAMPLES OF NON OHMIC CONDUCTORS:
Valves
Diodes
Transistors
Gases
Rectifiers
SOME ELECTRICAL CIRCUIT SYMBOLS:
Electric current is the time rate of flow of electric charge along a conductor. Current is produced when an electric charge flow from one point to another in a circuit. The s.i .unit of current is ampere and the symbol is A. For current, I is used.
FORMULA FOR CALCULATING CURRENT:
Current I = Charge measured in Coulomb / time measured in seconds.
Current = charge / time
APPLICATION OF FORMULA TO SOLVE PROBLEMS:
EXAMPLES:
*Calculate the current generated when 250 coulomb of charge flow in a circuit for 3½ minutes.
SOLUTION:
Data given in the question:
Charge = 250 Coulomb, time = 3½ minutes = 3½ * 60 seconds = 10/2 * 60 seconds = 10 * 30 seconds
Time = 300 seconds.
Formula: Current I = charge / time
Substitution: Current I = 250 Coulomb / 300 seconds
Current I = 0.833 ampere
*Given that the current that is generated in a circuit for 5½ minutes when a given quantity of electric charge flows through a conductor is 1.25 A, determine the charge.
SOLUTION:
Data given in the question:
Current I = 1.25 ampere, time t = 5½ minutes = 5½ * 60 seconds = 11/2 * 60 seconds = 11 * 30 seconds
Time = 330 seconds.
Formula: current I = Charge / time
Substitution: 1.25 = charge / 330
Make charge the subject of the formula: charge = 1.25 * 330
Charge Q = 412.5 Coulomb
*Calculate the time for which 3000 Coulomb of charge will generate 2.25 A of current in a circuit.
SOLUTION:
Data given in the question:
Charge Q = 3000 Coulomb, current I = 2.25 Amperes
Formula: current I = charge / time
Substitution: 2.25 = 3000 / time
Make time the subject of formula : time = 3000 / 2.25. Time = 1333.33 seconds
AMPERE:
Ampere can be defined as the flow of one Coulomb of charge in one second. It is the unit of current.
COULOMB:
Coulomb is defined as the quantity of electricity that flow through a conductor in one second when the current through the conductor is one ampere. Coulomb is the unit of charge.
AMMETER:
Ammeter is an instrument that is used for measuring current. Ammeters that can detect and measure small current are called milliameters. Galvanometers are ammeters that can detect and measure very small current.
SENSITIVITY OF AMMETER:
An ammeter is said to be sensitive if it can detect and measure a very small current or detect and measure current no matter how small the current may be.
CONNECTION OF AMMETER:
Ammeters are connected in series in a circuit so that the current the ammeters are to measure will flow through the ammeter themselves.
ACCURACY OF AMMETERS:
Ammeters are said to be accurate if it can detect and measure the exact amount of current that flows through it or if the current it detect and measure is very close to the value of current that flows through it.
ELECTRIC CIRCUIT:
Electric circuit is the Path through which electric current flows in a circuit. It consist of the source of electric energy connected through a conductor to a load and a switch.
TYPES OF ELECTRIC CIRCUITS:
Closed circuit:
A closed circuit is a circuit that is in the on position. In a closed circuit, the current flows through an external resistor. The resistor can be a bulb or any alliance connected in the part of the current.
DIAGRAM OF CLOSED CIRCUIT:
OPEN CIRCUIT:
An open circuit is a circuit that is in the off position. In an open circuit, the battery maintain no current in an external resistor and the bulb.
DIAGRAM OF OPEN CIRCUIT:
Short circuit:
A short circuit is a closed circuit that has no load connected to it.
DIAGRAM OF A SHORT CIRCUIT:
POTENTIAL DIFFERENCE P.D:
For electric current to flow in a circuit, there must be a pressure difference between the two points in the electric field. This pressure difference is the potential difference.
DEFINITION OF POTENTIAL DIFFERENCE:
The potential difference between any two points in an electric field is the work that is done in moving a positive charge of one Coulomb from one point to another in an electric field.
It can also be defined as the electrical pressure difference between the two points in an electric field. Potential difference is measured in volt, (V).
ELECTROMOTIVE FORCE EMF:
Electromotive force is the total work done in driving one coulomb of electric charge round a circuit. Of can also be defined as the total energy per Coulomb obtained from a cell. The unit of emf is volt, V. Emf can also be defined as joule per Coulomb.
FORMULA FOR CALCULATING EMF:
Electromotive force emf ( E ) = work done in joule / charge in Coulomb.
Recall that Current I = Charge Q / time t. charge q = current I * time t ( Q = I * t )
We can bring in this formula into the formula of electromotive force. Therefore,
Electromotive force = work done / ( current* time )
If emf is measured in volt, work in joule and charge in Coulomb, then
Volt = joule / Coulomb
APPLICATION OF FORMULA IN SOLVING PROBLEMS:
EXAMPLES:
*Calculate the work done by a cell of emf 12.5 volt if a charge of 250 Coulomb is maintained in the circuit.
SOLUTION:
Data given in the question:
Emf = 12.5 Volt, charge = 250 Coulomb, work = ?
Formula: emf = work ( w ) / charge( q )
Substitution: 12.5 = work / 250
Make work the subject of the formula: work = 12.5 * 250. work = 3125 joules.
*320 joules of work is done in electrical circuit. If the charge that flow in the circuit is 1250 Coulombs, determine the electromotive force of the cell in the circuit.
SOLUTION:
Data given in the question:
Work done = 250 Joules, Charge = 1200 Coulombs, electromotive force = ?
Formula: electromotive force = work done / charge
Substitution: emf = 250 / 1200 . emf = 0.208 volt.
DIFFERENCE BETWEEN EMF AND P.D:
Electromotive force is the potential difference between the terminal of a cell when it is not delivering any current in an external circuit or when they cell is in an open circuit.
While potential difference two points is the work done In moving one coulomb of electricity from one point to the other. The unit of potential difference is volt.
PRODUCTION OF ELECTRIC CURRENT:
Electric current can be produced from the following:
Chemical energy
Heat energy,
Mechanical energy
Solar energy
1..PRODUCTION OF ELECTRICITY FROM CHEMICAL ENERGY:
Electricity is produced from chemical energy through the use of cells.
CELL:
A cell is a chemical pack that produced is a chemical pack that produces current due to irreversible chemical reagle.
COMPONENTS OF A CELL:
A cell consist of positive anode and negative cathode that are separated by solution of various acid or salts.
ELECTRODES:
Electrodes are the positive and negative terminals of a cell. Current leaves the cell through the positive electrode and enters the cell through the negative electrode.
TYPES OF ELECTRODES:
There are two types of electrodes. They are :
The Anode
The Cathode
THE ANODE:
Anode the positive electrode / terminal of the cell. Current leaves the cell through the anode.
THE CATHODE:
The cathode is the negative terminal of the cell. Current enters the cell through the cathode.
ELECTROLYTE:
Electrolyte is the chemical composition of the cell in which the electrodes are immersed. The electrolyte is in a molten form so the that the electrons would be able to move about and constitute current.
SIMPLE CELL:
A simple cell consist of a copper rod as the positive anode and a zinc plate as the negative cathode immersed in a container that is filled with dilute sulphuric acid ( tetraoxosulphate (vi) acid ).
DIAGRAM OF A SIMPLE CELL:
WORKING PRINCIPLE OF A SIMPLE CELL:
When the switch is closed so that the copper and the zinc plates are connected together, the zinc slowly dissolves in the acid by chemical reaction. Electrons and bubbles of hydrogen gas are produced. The electrons flow through the wires from the zinc to the copper and produce current while the bubbles of hydrogen gas are formed on the copper anode of the cell.
CONVECTIONAL FLOW OF CURRENT:
In a cell, current flow from the positive anode to the negative cathode while electrons flow from the negative cathode to the positive anode. This opposite movement of current and electrons icps called convectional flow.
DEFECTS OF SIMPLE CELL:
Simple cell can only supply current for a short time due to its defects that is discussed below:
POLARIZATION:
Polarization defect is due to the formation of hydrogen gas bubbles on the copper anode of the cell. The hydrogen gas bubbles cover the copper anode and set up a back emf which oppose the forward emf of the cell. The back emf gradually reduces the current in the external circuit and eventually stop the chemical action of the cell which in turn stop the cell from working.
PREVENTION OF LOCAL ACTION:
Polarization defect can be prevented by the addition of chemicals called depolarizers such as manganese dioxide and potassium dichromate to the electrolyte.
FUNCTION Or ACTION OF DEPOLARIZERS:
The depolarizers oxidizes the hydrogen gas bubbles to form water.
LOCAL ACTION:
Local action is the wearing away of the zinc plate into the acid. Local action is due to the present of impurities such as iron and carbon in the zinc. The impurities set up tiny cells around the zinc surface and produce hydrogen bubbles on the zinc surface.
PREVENTION OF LOCAL ACTION:
Local action defect can be prevented by the process of amalgamation. Amalgamation is the rubbing of the zinc plate with mercury. The mercury prevents the impurities from touching or coming in contact with the acid and therefore prevent local action.
2.. PRODUCTION OF ELECTRICITY FROM HEAT ENERGY ( THERMOELECTRIC EFFECT ):
Electricity can be produced from heat using a thermocouple. Electricity is when there is a difference in temperature between the hot junction and cold junction of the thermocouple.
THERMOCOUPLE:
A thermocouple consist of a copper and iron wires at one end and the free ends are connected to a galvanometer.
DIAGRAM OF THERMOCOUPLE:
WORKING PRINCIPLE OF THERMOCOUPLE:
A thermocouple has a cold junction and hot junction. When the hot junction is immersed in hot water so that there is a difference in temperature between the hot junction and the cold junction, current flow in the wire of the thermocouple. The current is detected and measured be a galvanometer connected to the free ends of the two different wires. The higher the difference in temperature between the hot junction and the cold junction, the larger the current produced by the thermocouple.
THERMOELECTRICITY AND THERMOELECTRIC EFFECT:
Thermoelectricity is the electricity that is produced by a thermocouple while the effect that produced the current is called thermoelectric effect.
3..PRODUCTION OF ELECTRICITY FROM MECHANICAL ENERGY:
Electricity is produced from mechanical energy when a coil of insulated wire moves and cut across the magnetic field of a magnet. Current is induced in the coil and is tapped out through the split rings/ commutator and carbon brushes to which the ends of the coils are connected. The device is called generator or dynamo
AC GENERATOR:
An ac generator is a device that convert mechanical energy into electrical energy when a coil move and cut across the magnetic field of a magnet.
CONSTRUCTION OF AC GENERATOR:
An AC generator consist of a coil placed in the magnetic field of a north and south poles of a magnet. The ends of the coil are connected to two slip rings. The rings are connected to two carbon brushes. Current is tapped out through the two carbon brushes by wires connected to them.
4.. PRODUCTION OF ELECTRICITY FROM SOLAR ENERGY:
Electricity can be produced from solar energy. The device that is used is called photoelectric cell or photo cell.
PHOTO CELL:
A photo cell is a device that convert solar energy of the sun into electrical energy or electricity. It consist of a photosensitive surface metal such as potassium and alkaline metal that emits electrons when light incident on it.
DIAGRAM OF PHOTO CELL:
WORKING PRINCIPLE OF PHOTO CELL:
A photo cell consists of a light sensitive metal surface. When solar ( light ) energy from the sun incident on the metal surface, the metal surface emits electrons by photoelectric effect. The emitted electrons then flow in the circuit and constitute the current which is detected and measured by a galvanometer connected in the circuit.
THE ELECTRIC CIRCUIT:
I have discussed electric circuit before now. Here, I will center on some components that are commonly found in electric circuit.
As I defined earlier, electric circuit is that which electric current flows in a circuit. A circuit usually consist of cell which is the source of electric energy, a switch, an ammeter which measure the current that flow in the circuit, a voltmeter which measure the potential difference across a component, a resistor which is the load, a rheostat which is used to adjust the
AMMETER:
An ammeter is used to measure current that flow in a circuit. It has a small resistance. It is connected in series in the circuit so that the current it will measure should flow through it.
CIRCUIT CONNECTION DIAGRAM:
VOLTMETER:
A voltmeter is used to measure the voltage or potential difference across a component in a circuit. It has a large resistance. It is connected in parallel across the component whose voltage drop is to be determined. It takes in negligible amount of current.
CIRCUIT CONNECTION DIAGRAM:
RESISTOR:
A resistor is an electrical component that oppose the flow of electric current through itself.
STANDARD RESISTOR:
A standard resistor is a resistor whose resistance is known and fixed. Standard resistor is usually in the form of length of resistance wire or a piece of carbon.
Constantan or manganin are used for making standard resistors because their resistances is are little affected by temperature change.
VARIABLE RESISTOR OR POTENTIOMETER:
A variable resistor is a resistor whose resistance is not fixed. It is a resistor that has different values of resistance. The resistance of a variable resistor can be changed to any desired value. Rheostat is an example of variable resistor.
RESISTANCE:
Resistance is the opposition that a resistor offered to the flow of electric current through itself. The unit of resistance is ohm.
DEFINITION OF OHM:
Ohm is defined as the resistance of a conductor when a potential difference or a voltage of one volt is applied across the conductor causes a current of one ampere to flow through the conductor. The symbol used to represent ohm is ...
NON OHMIC MATERIALS:
Non ohmic materials or conductors are those materials or conductors that do not obey ohms law. They are materials in which the current that flow through them do not increased as the voltage connected across them is increased.
EXAMPLES OF NON OHMIC CONDUCTORS:
Valves
Diodes
Transistors
Gases
Rectifiers
SOME ELECTRICAL CIRCUIT SYMBOLS:
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