Question | Answer |
A current will flow through an electrical component only if there is . . . | a VOLTAGE or POTENTIAL DIFFERENCE (p.d.) across its ends. |
The bigger the potential difference across a component . . . | The bigger the CURRENT that flows through it. |
Components resist a current flowing through them. The bigger their resistance . . . | The smaller the current produced by a particular voltage |
The p.d. across a component in a circuit is measured in . . . | VOLTS |
Voltage (p.d.) is measured using . . . | a VOLTMETER connected IN PARALLEL with the component. |
The CURRENT flowing through a component in a circuit is measured using . . . | an AMMETER connected IN SERIES with the component. |
The unit of current is . . . | the AMPERE (AMP) |
A current of 1 A is equal to a charge flowing of . . . | 1 COULOMB per SECOND |
In metals, a current is a flow of charged particles called . . . | ELECTRONS |
In a circuit, we say that Conventional Current always flows from . . . | The POSITIVE terminal of a cell, towards the NEGATIVE terminal. |
In metals, electricity is actually carried by NEGATIVELY charged electrons, which flow from . . . | the NEGATIVE terminal towards the POSITIVE terminal of a cell. |
The behaviour of a component in a circuit can best be studied by plotting . . . | a current-voltage graph. |
A resistor at constant temperature has a constant ratio of . . . | current to voltage. Its graph is a straight line. |
The current-voltage graph for a filament lamp is NOT a straight line. The reason is . . . | Resistance increases as temperature increases. |
A diode is a device which . . . | only allows a current to flow one way through it. |
When components are connected in series . . . | the SAME CURRENT flows through each component. |
The total resistance of components in series is . . . | equal to the SUM of their separate resistances. |
The total potential difference in a series circuit is . . . | shared between the individual compoents. |
If a p.d. of 12 volts is shared between two equal resistances, each one will get . . . | 6 volts. |
If a p.d. of 12 volts is shared between two resistors of 6 ohms and 12 ohms, the bigger resistor will get . . . | 8 volts. ( The smaller one gets 4 volts because it has half the resistance of the other one.) |
When components are connected IN PARALLEL . . . | There is the SAME p.d. across each component. |
The total current in a parallel circuit is equal to . . . | the SUM of the currents through each of the separate components. |
If one lamp is connected to a cell it gets a current of 1 amp. If two identical lamps are connected in parallel (to the same cell) they will get . . . | a current of 1 amp each - that makes the total current 2 amps. |
If one lamp gets a current of 1A from one cell, two lamps joined in series will get . . . | approximately half as much current ( 0.5A) because they have twice as much resistance. |
The p.d. provided by cells connected in series is equal to . . . | the SUM of the p.ds. of each cell separately bearing in mind the direction in which they are connected. |
The resistance of a component is measured in… | OHMS |
Potential difference, current and resistance are related by Ohm's Law which states… | P.d. = current x resistance |
The resistance of a component is calculated by applying Ohm's law as follows: | R = Voltage / current |
If a current of 2A flows in a resistor of resistance 10 ohms, the p.d. across the resistor is . . . | 20 volts |
What is the current when a p.d. of 12v is applied across a 10 ohm resistor? | 1.2 A |
The current through a resistor at constant temperature is . . . | directly proportional to the p.d. across the resistor. |
A lamp converts electrical energy into . . . | light and heat. |
When electric charge flows through a resistor, electrical energy is transferred as . . . | HEAT |
The rate of energy transfer is called . . . | POWER |
Power is measured in watts. 1W is equal to . . . | 1 joule per second |
In an electric circuit, POWER = | P = I V |
Energy transferred = | E = P x t |
CHARGE (coulomb) = | Current x Time |
Metals are good conductors of electricity because . . . | some of their electrons can move freely throughout the metal. |
When two different materials are rubbed together . . | electrons are transferred from one to the other |
Certain materials can be used as electrical insulators. This is because . . . | they do not conduct electricity |
When a substance loses electrons, it becomes . . . | POSITIVELY charged. |
Opposite electric charges will . . . | ATTRACT each other |
Like charges . . . | REPEL each other |
A charged object can be discharged by . . . | connecting it to EARTH with a conductor |
When walking along a nylon carpet with plastic-soled shoes, you may pick up a static charge. This happens because . . . | electrons are transferred by friction from the shoes to the carpet |
When you touch a metal door handle you sometimes receive an electric shock because . . . | a charge passes from your body to earth through the door handle |