P5

Question 1

How are devices that use plugs and devices that use batteries different (Batteries use DC current)

Answer 1

-Battery devices can be used anywhere but plugged devices must be used near a plug
-Batteries transfer energy from chemical ptotential by electric current, plugs directly supply electrical energy

Question 2

How aee devices that use plugs and devices that use batteries the same?c (plugges devices use AC CURRENT)

Answer 2

• both transfer energy to electrical devices
• both must be connected to the device

Question 3

AC means

Answer 3

Alternating current

Question 4

DC means

Answer 4

Direct current

Question 5

Direct current means

Answer 5

The current flows in one direction only

Question 6

Alternating current means

Answer 6

The current constantlg changes direction, how often is called frequency

Question 7

DC examples

Answer 7

Cells, batteries

Question 8

AC examples

Answer 8

Mains supply, power socket

Question 9

DC current on a graph maintains a

Answer 9

Constant voltage due to the singke direction current flow

Question 10

AC current on a graph constantly

Answer 10

Reverses its voltage (up and down) due to the current constsntly changing direction (freauency)(Hz)

Question 11

Mains electricity

Answer 11

An alternating current

Question 12

In the UK mains electricity is about

Answer 12

230 V

Question 13

In the Uk mains electricity has a frequency of

Answer 13

50Hz

Question 14

Transmitting electricity at a high voltage reduces power loss, making

Answer 14

The system more efficient

Question 15

Step-up transformer

Answer 15

Increases the voltage, but decreases the current

Question 16

Step- down transformer

Answer 16

Decreases the voltage, increases the current

Question 17

Power station function

Answer 17

Burns fuel - heats water - steam - turn turbine - turn generator - generate electricity

Question 18

Electricity is dustributed via the

Answer 18

National grid

Question 19

The national grid is a gaint susten if

Answer 19

Cables and transformers that civer the UK and connects power stations to consumers

Question 20

Disadvantages of underground cables

Answer 20

• very expensive (miles and miles of cable)
• lots of digging
• maintenance is hard, must dig them up
• cables get hot, hard too cool (underground). Must be thicker
• would need to clearky mark where they are in order for no one to dig them up.

Question 21

What are the ads and dis of overhead cables?

Answer 21

• relativelt cheap to link between tall towers
• easy access to maintain cables
• open to air cooling of cables

Dis:

• ugly, ruin landscapes
• vulnerable to weather
• must cut across large amount of land

Question 22

How do fuses work?

Answer 22

-The fuse breaks the circuit if a fault in an appliance causes too much current flow.
-This protects the wiring and the appliance if something goes wrong.
-The fuse contains a piece of wire which melts easily.
-If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.

Question 23

Fuses in plugs are made in standard ratings. The most common are:

Answer 23

3 A, 5 A and 13 A.
-The fuse should be rated at a slightly higher current than the device needs:
• If the device works at 3 A, use a 5 A fuse
• If the device works at 10 A, use a 13 A fuse

Question 24

Residual current circuit breakers, RCCBs, protect some circuits. They detect a difference

Answer 24

in the current between the live and neutral wires. RCCBs work much faster than fuses do.

Question 25

Live wire

Answer 25

• brown
• provides the alternating difference from the mains supply.

Question 26

Nuetral wire

Answer 26

• Blue
• nuetral wire completes the circuit.
• when the appliance is operating normally, current flows through the live and nuetral wire - around 0 V

Question 27

Power, energy transferred, time

Answer 27

Energy (J’) = power (W) x time (s)

E =. Pt

Question 28

Earth wire

Answer 28

• green and yellow
• for protecting the wiring
• and for safety
• stops the appliance casing from becoming live
• doesn’t usually carry a current - only when there’s a fault, at 0 V

Question 29

Watts (W) = Joules per second (J/s)

Answer 29

1W = 1 J/s

Question 30

Power, potential difference, current

Answer 30

Power (W) = potential difference (V) x Current (A)
P = V X I

Question 31

Power, current, resistance

Answer 31

P = I (squared) X Resistance

Question 32

Current, coulomb, time

Answer 32

Current (A) = Coulomb (charge flow, C) DIVIDED BY time (s)

Question 33

A (amps) = Coulombs per second (C/s)

Answer 33

1 A = 1 C/s

Question 34

Energy transferred, charge flow, potential difference

Answer 34

Energy transferred (j) = charge flow(C) X Potential difference( (V)