topic 2 - electricity

Question 1

unit for current

Answer 1

amperes (A)

Question 2

unit for charge

Answer 2

coulombs (C)

Question 3

unit for resistance

Answer 3

ohms (Ω)

Question 4

unit for time

Answer 4

seconds (s)

Question 5

unit for potential difference

Answer 5

volt (V)

Question 6

unit for power

Answer 6

watt (W)

Question 7

how do fuses help protect

Answer 7

Stop the flow of current by melting if the current is too high, protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.

Question 8

how do circuit breakers help protect

Answer 8

break the circuit if current is too high.

Question 9

how do insulation and double insulation help protect

Answer 9

prevent people from touching exposed wires and getting shocks.

Question 10

how does earthing help protect

Answer 10

provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.

Question 11

what can resistance cause a transfer of

Answer 11

electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens e.g. electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced

Question 12

relationship between power, current and voltage

Answer 12

power = current x voltage

P = I x V

Question 13

energy transferred, current, voltage and time

Answer 13

energy transferred = current x voltage x time

E = VIt

Question 14

what is alternating current

Answer 14

AC is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.

Question 15

what is direct current

Answer 15

DC is constant. And is produced from a battery and used in some sensitive components like in computing.

Question 16

3 advantages of parallel circuits

Answer 16

• Components (e.g. bulbs) may be switched on/off independently.
• If one component breaks, current can still flow through the other parts of the circuit.
• Bulbs maintain a similar brightness.

Question 17

2 advantages of series circuits

Answer 17

• Fewer wires, cheaper and easier to assemble.
• Uses less power

Question 18

what is the relationship between voltage and resistance

Answer 18

as voltage increases, resistance also increases

Question 19

qualitative effect of changing resistance on the current in a circuit

Answer 19

Since V = IR, as you increase the resistance in a circuit, the current will decrease.

Question 20

qualitative variation of resistance of light-dependent resistors (LDRs) with illumination

Answer 20

as illumination increases, resistance decreases

Question 21

qualitative variation of resistance of thermistors with temperature

Answer 21

as temperature increases, resistance decreases

Question 22

how can LED’s be used to show current in a circuit

Answer 22

A lamp can be added to a circuit to check for a current. If current is flowing, the lamp will light up.

Question 23

relationship between voltage, resistance and current

Answer 23

voltage = resistance x current

V = IR

Question 24

what is current

Answer 24

rate flow of charge

Question 25

relationship between charge, current and time

Answer 25

charge = current x time Q = It

Question 26

what are electrons in a solid metal conductor like

Answer 26

Electrons are negatively charged and free to flow in a metal so carry charge

Question 27

why is current conserved at a junction in a circuit

Answer 27

At a junction current ‘splits’ to take both paths. It comes back together when the paths meet again.

Question 28

what is the voltage across two components connected in parallel

Answer 28

the voltage is the same

Question 29

relationship between voltage, energy transferred per unit passed and charge

Answer 29

voltage = energy transferred/charge V = E/Q