Electricity

Question 1

State the rule for current in a series circuit

Answer 1

the current is the same at every point in the circuit and in every component

Question 2

State the rule for potential difference in a series circuit

Answer 2

the total potential difference of the power supply is shared between components

Question 3

State the rule for resistance in a series circuit

Answer 3

the more resistors, the greater the resistance. RT=R1+R2

Question 4

State the rule for current in a parallel circuit

Answer 4

the total current through the whole circuit is the sum of the currents through the separate components

Question 5

State the rule for potential difference in a parallel circuit

Answer 5

the potential difference across each branch in the circuit is the same

Question 6

State the rule for resistance in a parallel circuit

Answer 6

adding more resistors in parallel decreases resistance

Question 7

What colour is the live wire in a three core cable?

Answer 7

brown

Question 8

What colour is the neutral wire in a three core cable?

Answer 8

blue

Question 9

What colour is the earth wire in a three core cable?

Answer 9

green and yellow

Question 10

The brown wire in a plug is the _______

Answer 10

live

Question 11

The blue wire in a plug is the ________

Answer 11

neutral

Question 12

The green and yellow wire in a plug is the ________

Answer 12

earth

Question 13

The potential difference between the live wire and others in the plug is _____ V

Answer 13

230V

Question 14

Current flows into an appliance through the _______ wire

Answer 14

live

Question 15

Current flows out of an appliance through the ______ wire

Answer 15

neutral

Question 16

The _________ wire is a safety feature of appliances

Answer 16

earth

Question 17

Potential difference between the neutral wires and others in the plug should be ____ V

Answer 17

0V

Question 18

Electric Current is….?

Answer 18

the flow of electric charge

Question 19

Potential difference between two points in a circuit is….?

Answer 19

the work done when a couloumb of charge passes between the points.

Question 20

In a circuit the potential difference causes …..?

Answer 20

charge to flow

Question 21

Resistance is…?

Answer 21

caused by anything which opposes the flow of electric charge

Question 22

Particles which can be ‘charges’ in electric circuits are…

Answer 22

electrons or ions

Question 23

What is a series circuit?

Answer 23

A circuit with only one route for charge to flow

Question 24

What is a parallel circuit?

Answer 24

A circuit with more than one route for charge to flow

Question 25

State the equation which links charge flow, current and time

Answer 25

Q=It

Question 26

State the equation which links current, potential difference and resistance

Answer 26

V=IR

Question 27

State the equation which links current, potential difference and power

Answer 27

P=IV

Question 28

State the equation which links current, power and resistance

Answer 28

P=I2R

Question 29

State the equation which links energy transferred, power and time

Answer 29

E=Pt

Question 30

State the equation which links charge flow, energy transferred and potential difference

Answer 30

E=QV

Question 31

What is the unit of charge flow?

Answer 31

Coulomb ( C )

Question 32

What is the unit of current?

Answer 32

Amps (A)

Question 33

What is the unit for potential difference?

Answer 33

Volts (V)

Question 34

What is the unit for resistance?

Answer 34

Ohms (Ω)

Question 35

What is the unit for power?

Answer 35

Watts (W)

Question 36

Describe the I-V characteristic for a fixed resistor

Answer 36

Current and potential difference are directly proportional, resistance is constant

Question 37

Describe the I-V characteristic of a filament lamp

Answer 37

Resistance is not constant, it increases as p.d. increases

Question 38

Explain why resistance increases with increased p.d. in a filament lamp

Answer 38

temperature increases causing ions to vibrate and increasing collisions with electrons flowing through the filament

Question 39

Describe the I-V characteristic of a diode

Answer 39

The current only flows through the diode in one direction, there is a very high resistance in the reverse direction.

Question 40

Current which regularly changes direction is called…

Answer 40

alternating current

Question 41

An example of alternating current is…?

Answer 41

mains electricity

Question 42

Current which flows in one direction is…?

Answer 42

direct current

Question 43

An example of direct current is…

Answer 43

batteries

Question 44

What is the potential difference of mains electricity in the UK?

Answer 44

230V

Question 45

What is the frequency of the alternating current in UK mains electricity?

Answer 45

50Hz

Question 46

The national grid consists of…?

Answer 46

Cables and transformers

Question 47

Are power stations par of the national grid?

Answer 47

no

Question 48

What does a step up transformer do?

Answer 48

Increases p.d.

Question 49

What does a step down transformer do?

Answer 49

reduces p.d. to 230 V

Question 50

Why are transformers used?

Answer 50

reduce current so that less heat is lost in cables, increases efficiency