Current Electricity

Question 1

Current

Answer 1

Rate of flow of charge

Question 2

Coulomb

Answer 2

Unit of charge. If one amp flows for one second then one coulomb of charge has passed

Question 3

Potential difference

Answer 3

Work done per unit charge ( joules/coulomb)

Question 4

Ammeter

Answer 4

Used to measure current, has zero resistance

Question 5

Voltmeter

Answer 5

Used to measure Potential difference. Ideally has infinite resistance

Question 6

Whenever charge flows through a component……

Answer 6

energy is transferred

Question 7

Ohmic conductor

Answer 7

Provided that temperature is constant, the current flowing through an ohmic conductor is proportional to the applied voltage

Question 8

Gradient of an I/V graph tells us …..

Answer 8

1/Resistance

Question 9

I/V for filament lamp

Answer 9

Produces a curved graph as resistance changes as more current flows. The current heats the filament causing resistance to increase

Question 10

Diode

Answer 10

Allow current to flow in one direction (forward bias)

Require a voltage of around 0.6V before they will conduct

Question 11

Threshold voltage

Answer 11

Minimum voltage needed for a diode to conduct Most diodes require a voltage of around 0.6V before they will conduct

Question 12

LDR

Answer 12

Light dependant resistor. The greater the light intensity, the lower the resistance. Light provides the energy needed to release more electrons (charge carriers)

Question 13

Thermistor

Answer 13

Resistance decreases with increasing temperature. Thermal energy provides electrons with energy needed to become free and thus a charge carrier

Question 14

Resistivity

Answer 14

A material property not a property of an object. How much a particular material resists the flow of current

Question 15

Superconductor

Answer 15

Materials that can exhibit zero resistance

Question 16

Critical temperature

Answer 16

The temperature below which a material becomes superconducting and has zero resistance

Question 17

Power

Answer 17

Rate of transfer of energy

Question 18

Watt

Answer 18

Unit of power, equal to one joule transferred per second

Question 19

Internal resistance

Answer 19

The resistance that all batteries and power sources have

Question 20

EMF

Answer 20

the amount of energy that the battery transfers to each coulomb of charge

Question 21

EMF is equal in magnitude to

Answer 21

The voltage across the components in the circuit plus the voltage dropped across the internal resistance of the battery

Question 22

The voltage across the components in a circuit (the terminal p.d) is equal to

Answer 22

The EMF minus the voltage dropped across the internal resistance

Question 23

The area under a graph of current against time is equal to

Answer 23

The total charge flow

Question 24

To find EMF from a graph of voltage against current you find the

Answer 24

Intercept of the line on the voltage axis

Question 25

Kirchoff’s first law

Answer 25

Total current entering a junction = total current leaving a junction

Question 26

Kirchoff’s second law

Answer 26

The total EMF around a series circuit = sum of the p.ds across each component in the circuit

Question 27

Potential divider

Answer 27

At it’s simplest, a circuit with a voltage source and two fixed resistors. The voltage is split between the two resistors so you can tap off different values of voltage

Question 28

Potentiometer

Answer 28

A potential divider with a variable resistor and a fixed resistor. It allows us to obtain any voltage from 0V to the supply voltage