Electricity and Circuits

Question 1

what is the difference between series and parallel circuits?

Answer 1

series- components connected in line, same current everywhere, p.d. shared
parallel- separately connected, same p.d., current shared

Question 2

what is potential difference?

Answer 2

energy transferred over unit charge

Question 3

what is a volt?

Answer 3

p.d. is sometimes called voltage, same thing

Question 4

what is the equation for energy transferred?

Answer 4

energy transferred= charge moved X potential difference

E= Q X V

Question 5

what is current?

Answer 5

• flow of electrical charge e.g. electrons
• only flow if there is is p.d.
• circuit must be complete

Question 6

what is the equation for charge?

Answer 6

charge= current X time
Q= I X T
current in A
Charge in C
Time in s

Question 7

what happens to current at a junction in a circuit?

Answer 7

current is conserved at a junction in a circuit

Question 8

what is resistance and what is it measured in?

Answer 8

anything that slows the flow down

measured in ohm

Question 9

what is the equation for potential difference?

Answer 9

potential difference= current X resistance

V= I X R

Question 10

what happens when you add a resistor in a series circuit?

Answer 10

• increases total resistance
• because they have to share total p.d.
• and the current is the same everywhere

Question 11

what happens when you add resistor in a parallel circuit?

Answer 11

• reduces total resistance

- increase in current meaning decrease in total resistance

Question 12

what is the current like in a series circuit?

Answer 12

-current same everywhere

I= V / R

Question 13

what is the potential different like in a series circuit?

Answer 13

-total p.d. of supply is equally shared

Question 14

what is the resistance like in a series circuit?

Answer 14

-increases as you add resistors

Question 15

what happens if one component isn’t working in a series circuit?

Answer 15

nothing will work

Question 16

what is the method of practical used to investigate the relationship between V, I, and R for resistor and filament lamps?

Answer 16

1. set up circuit with ammeter, cell, resister, and voltmeter under component
2. change resistance and measure current
3. take several pair of readings
4. plot current against p.d. on I-V graph
5. you can then see relationship

Question 17

what happens when you add a diode as the component in the circuit?

Answer 17

if you swap its direction current cannot flow through it

Question 18

what happens when you add a thermistor as the component in the circuit?

Answer 18

as you heat it current increases and resistance decreases

Question 19

what happens when yours LDR’s (filament lamps) as the component in the circuit?

Answer 19

light will get brighter, current increases and resistance decreases

Question 20

what happens when there is an electric current in a resistor?

Answer 20

there is an energy transfer which heats the resistor

Question 21

LEARN GRAPHS ON PAGE 187

Answer 21

LEARN GRAPHS ON PAGE 187

Question 22

what equation can we use to work out energy transferred to and electrical component?

Answer 22

E= I X V X t

Question 23

what are the advantages of the heating effect on an electrical circuit?

Answer 23

• toasters, containing a coil of wire

- similar to filament bulbs and electric heaters

Question 24

what are the disadvantages of the heating effect on an electrical circuit?

Answer 24

• reduces efficiency

- too high, could melt

Question 25

what is power? what is it measured in?

Answer 25

- energy transferred per second | - measured in watts

Question 26

what is the equation for power?

Answer 26

``` P= E/t power(W)= energy transferred(J) / Time(s) ```

Question 27

how is the power transfer in a circuit related to the potential different and current in it?

Answer 27

- p.d. tells you energy each unit of change transfers - currents tells you how much charge passes per unit time - so both effect energy transferred to appliance

Question 28

what is the equation for electrical power?

Answer 28

-P= I X V e.p. (W)= current(A) X p.d.(V) OR -P= I2 X R e.p.(W)= current squared (A) X resistance (ohm)

Question 29

what is direct current?

Answer 29

-charges move in same direction

Question 30

what is alternating current?

Answer 30

-charges constantly changing direction

Question 31

what supplies direct current?

Answer 31

cells and batteries

Question 32

what is the UK domestic electric supply (d.c. or a.c.) and whats the voltage and frequency?

Answer 32

- alternating current - frequency= 50Hz - voltage= 230V

Question 33

what is the function of a live wire in a plug?

Answer 33

- brown - carries voltage - around 230V

Question 34

what is the function of a neutral wire in a plug?

Answer 34

- blue - completes circuit - generally electricity goes in live wire and out neutral wire

Question 35

what is the function of the earth wire in a plug?

Answer 35

- green/yellow - safety and protecting wiring - stop appliance becoming live

Question 36

what is the function of a fuse in a plug?

Answer 36

-prevent electrical overloads

Question 37

why should switches and fuses be connected in a live wire of a domestic circuit?

Answer 37

-so the current can be broken

Question 38

what is the function of a circuit breaker and why is it better than a fuse?

Answer 38

- will trip instead of melting fuse - turn off quicker - can be reset instead of replaced like a fuse

Question 39

what is the potential difference between live and earth wires?

Answer 39

230V

Question 40

what is the potential difference between the live and neutral wire?

Answer 40

230V

Question 41

what is the potential difference between the neutral and earth wire?

Answer 41

0V

Question 42

what are the potential dangers of the live wire and earth?

Answer 42

- electrical shock - fire - current flowing through body