Electricity

Question 1

Electric current

Answer 1

The flow of charge per unit time, or the rate of flow of charge.

Question 2

Potential Difference

Answer 2

The energy transferred per unit charge between two points in a circuit.

Question 3

Resistance

Answer 3

The measure of how difficult it is for charge carriers to pass through a component.

Question 4

Ohm’s law

Answer 4

For an ohmic conductor, current is directly proportional to the potential difference across it. Given the physical conditions across it remain constant.

Question 5

Ohmic conductor

Answer 5

Component that follows Ohm’s law.

Question 6

Semiconductor Diode

Answer 6

The forward bias of a diode is the direction in which it will allow current to flow easily past the threshold voltage, which is the smallest voltage needed to allow current to flow

Question 7

Filament lamp

Answer 7

Contains a length of metal wire which heats up as current increases, therefore the resistance of this component increases as the current increases.

Question 8

Resistivity

Answer 8

A measure of how easily a metal conducts electricity. product of resistance and cross-sectional area, divided by the length of the material.

Question 9

What happens when temperature increases in a metal conductor?

Answer 9

The resistance will increase.

Question 10

How do thermistors work?

Answer 10

• As the temperature of the thermistor increases, the resistance decreases.
• Increasing the temperature of the atom causes electrons to be emitted from atoms.
• Therefore, the number of charge carriers increases which increases the current which hence lowers the resistance.

Question 11

What is an application of a thermistor?

Answer 11

Trigger an event to occur when the temperature drops or reaches a certain value. e.g. heating in a room.

Question 12

Superconductor

Answer 12

A material which, below a certain temperature (known as the critical temperature) has zero resistivity.

Question 13

What are some applications of superconductors?

Answer 13

Power cables - reduce energy loss through heating to zero.
Strong magnetic fields - Maglev trains and medical applications.

Question 14

Resistors in series

Answer 14

RT = R1 + R2 + R3 ….

Question 15

Resistors in parallel

Answer 15

1/RT = 1/R1 + 1/R2 ….

Question 16

Power

Answer 16

The energy transferred over time.

Question 17

Current and PD in a series circuit

Answer 17

The current is the same everywhere in the circuit.
PD across all elements is equal to the supply PD (adds up to total).

Question 18

Current and PD in a parallel circuit

Answer 18

The sum of current across all components adds up to the total. (Adds up)
The PD is the same across each branch.

Question 19

What is conserved in DC circuits?

Answer 19

Charge and energy are always conserved.

Question 20

Kirchhoff’s first law

Answer 20

The total current flowing into a junction is equal to the current flowing out of that junction.

Question 21

Kirchhoff’s second law

Answer 21

The sum of all voltages in a series circuit is equal to the battery voltage.

Question 22

Potential divider

Answer 22

Several resistors in series connected across a voltage source, used to produce a required fraction of the source potential difference which remains constant.

Question 23

Variable resistor

Answer 23

Supplies a variable potential difference which will vary the resistance across it.

Question 24

Light dependent resistor (LDR)

Answer 24

A light dependent resistor’s resistance decreases as light intensity increases.

Question 25

Internal resistance

Answer 25

caused by electrons colliding with atoms inside the battery, therefore some energy is lost before electrons even leave the battery.

Question 26

Electromotive force (EMF)

Answer 26

The energy transferred by a cell per coulomb of charge that passes through it.

Question 27

Terminal PD

Answer 27

The p.d across the resistor R.

Question 28

Lost volts

Answer 28

p.d across the resistor r this value is equal to the energy wasted by the cell per coulomb of charge.