Electricity Booklet

Question 1

What is the definition of electric current?

Answer 1

The rate of flor of charge

Question 2

What is the equation that links charge current and time

Answer 2

Charge=current x time

Q=I x t

Question 3

What is the equation that links potential difference, current and resistance?

Answer 3

Potential difference= current x resistance

V=I x R

Question 4

What’s the difference between a series and parallel circuit?

Answer 4

A series circuit has only one path for the current to flow; a parallel circuit has more than one

Question 5

What does ohms law say?

Answer 5

The current though an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor

Question 6

What happens to the resistance of a filament lamp as the temperature increases?

Answer 6

As the temperature increases the resistance of a filament lamp also increases

Question 7

What happens to the resistance of a thermistor as it increases in temperature?

Answer 7

The resistance decreases as the temperature increases

Question 8

What happens to the resistor of a LDR as the light intensity increases?

Answer 8

The resistance decreases as the light intensity decreases

Question 9

In what diode can the current flow through a diode?

Answer 9

A current can only flow one way though a diode

Question 10

Name an application of an LDR/thermistor:

Answer 10

In sensing circuits ( lights turning on when dark/ heat turning on when cold)

Question 11

How does resistance add in series?

Answer 11

RTOT=R1+R2

Question 12

What happens to current in series/parallel circuits?

Answer 12

Current is the same everywhere in a series circuit. Current splits in a parallel circuit

Question 13

What happens to the potential difference in series/parallel circuits?

Answer 13

Potential difference is the same on different paths of a parallel circuit; it splits across components in a series circuit

Question 14

What happens to the total resistance of two resistors in parallel?

Answer 14

The total resistance of two resistors in parallel is less than the resistance of the smaller resistor

Question 15

What do we use to measure potential difference/current?

Answer 15

We use a voltmeter in parallel across a component and an ammeter in series.

Question 16

What is the frequency and potential difference of the mains electricity supply?

Answer 16

50Hz and 230V

Question 17

What is the difference between AC and DC

Answer 17

AC changes direction, DC remains in the same direction

Question 18

What are the colours of the live, neutral and earth wires?

Answer 18

Live-brown, neutral-blue, earth-green and yellow stripes

Question 19

What do the live, neutral and earth wires do?

Answer 19

Live wires carry the AC, neutral wires complete the circuits, earth wires is safety wire.

Question 20

What happens to the fuse if the current is too high?

Answer 20

The fuse melts making the circuit incomplete, stopping the current from flowing.

Question 21

Give two equations for electrical power:

Answer 21

P=I x V

P=I^2 x R

Question 22

Give two equations for energy transfer:

Answer 22

E=P x t

E=Q x V

Question 23

What is the national grid?

Answer 23

A network of cables and transformers linking power stations and consumers together

Question 24

What does a step-up transformer do?

Answer 24

It increases the potential difference but decreases the current to reduce heat loss in cables

Question 25

What does a step-down transformer do?

Answer 25

It decreases the potential difference to a safe level for consumers

Question 26

What is potential difference?

Answer 26

The difference on the amount of energy that charge carriers have between two points in a circuit. E=Q x V

Question 27

What is the definition of power?

Answer 27

A measure of how quickly energy is transferred from one form to another. P=E/t