Electricity

Question 1

Charge equation

Answer 1

Q (charge in coulombs)= I (current in amps) x t (time in secs)

Question 2

Metal Wire (structure)

Answer 2

Positive lattice ions in fixed positions that vibrate and free electrons

Question 3

Current

Answer 3

Current is defined as the rate of flow of charge from one place to another

Question 4

Current requirements

Answer 4

A complete circuit and a source of potential difference

Question 5

Factors affecting current

Answer 5

The size of the current depends on the potential difference and resistance of the circuit

Question 6

Current equation

Answer 6

I (current, amps)= V (voltage, volts) /R (resistance, ohms)

Question 7

Potential difference

Answer 7

Also known as voltage, defined as the energy transferred when one coulomb of charge

Question 8

Resistance cause

Answer 8

Resistance is caused by collisions between electrons and positive lattice ions

Question 9

Resistance increases because…

Answer 9

The wire is thinner or longer, the current increases causing more collisions

Question 10

Diodes

Answer 10

Has a large resistance in one direction so current can only flow through it in the other direction (forwards bias)

Question 11

Series circuit

Answer 11

There is only one route from one side of the battery to the other (however if only a voltmeter is connected in parallel the circuit is still series)

Question 12

Parallel ciruit

Answer 12

There are at least 2 routes from one side of the battery to the other

Question 13

How to find current into a junction

Answer 13

The total current into a junction is equal to the total current out

Question 14

How to find P.d. in circuits

Answer 14

The total p.d. into a closed loop is equal to the total p.d. used up around that loop

Question 15

Resistors in series vs parallel

Answer 15

Resistors connected in series have a higher resistance

Question 16

Power equations (2)

Answer 16

P (power in watts)= I (amps) x R (ohms)

P (Watts in W)= I (Amps in A) x V (Volts in V)

Question 17

Energy equation

Answer 17

E (Joules, J)= P (Watts, W) x t (time, s)

Question 18

AC

Answer 18

Alternating current meaning electrons go back and forth, used in household electricity

Question 19

DC

Answer 19

Direct current meaning electrons travel one way, used in batteries or power packs

Question 20

Frequency of mains electricity?

Answer 20

50 hertz (Hz)

Question 21

How to get voltage from a P.d. graph

Answer 21

Distance from resting electron position to top of peak

Question 22

Voltage of UK main supply

Answer 22

230V

Question 23

Frequency equation

Answer 23

f (waves/s in Hz)= 1/T (time period in s)

Question 24

How does a fuse work?

Answer 24

A fuse protects the appliance by melting if too much current flows through it thus breaking the circuit

Question 25

3 types of wires in a plug

Answer 25

The earth, live and neutral wires

Question 26

National Grid

Answer 26

The national grid if a system of cables and transformers that transfer electrical power from power stations to consumers

Question 27

National Grid Problem

Answer 27

The main problem is the heating effect of the current in the cables meaning energy is lost to the surroundings

Question 28

What do transformers do?

Answer 28

Improve efficiency of electrical power transfer

Question 29

Step-up transformer

Answer 29

Increase p.d. and decrease current meaning less energy is wasted heating surroundings

Question 30

Step-down transformer

Answer 30

Does the opposite of a step-up just before reaching homes and factories

Question 31

3 energy pathways

Answer 31

heating, work done by forces or work done by electrical currents

Question 32

Energy (gravitational)

Answer 32

E= m x g x h

Question 33

Energy (elastic)

Answer 33

E= 1/2 x k x e^2

Question 34

Kinetic energy equation (velocity)

Answer 34

E= 1/2 x m x v^2