Electricity

Question 1

What is current

Answer 1

The rate of flow of charge round an electric circuit

Question 2

What happens to the current if the resistance is higher

Answer 2

The higher the resistance the lower the current for a fixed p.d

Question 3

Equation for charge

Answer 3

Q=It

Question 4

Equation for p.d

Answer 4

V=IR
V = E/Q

Question 5

What happens to the resistance in Ohmic conductors as current changes

Answer 5

It doesn’t change

Question 6

What is the IV characteristics of an ohmic conductor

Answer 6

Current is directly proportional to the p.d

Question 7

What is the IV characteristic of a filament lamp

Answer 7

‘F’ like
As temperature increases, resistance increases therefore less current can flow hence the curve

Question 8

What is the IV characteristic of a diode

Answer 8

Exponential like
Current will only flow through the diode in one direction
The diode has a very high resistance in the opposite direction

Question 9

What is the IV characteristic of a Light-dependent resistor

Answer 9

Decreasing resistance as light increases
Used in automatic night lights

Question 10

What is the IV characteristic of a Thermistor

Answer 10

Decreasing resistance as temperature increases
Used in car engine temperature sensors and electronic thermostats

Question 11

What is the equivalent resistance in parallel circuits

Answer 11

The resistance of one resistor/ The no. of resistors

Question 12

How does the no. of identical resistors affect a series circuit

Answer 12

Increases resistance

Question 13

How does the no. of identical resistors affect a parallel circuit

Answer 13

Decreases resistance

Question 14

What is the frequency of A.C mains supply

Answer 14

50hz

Question 15

What colour and what does the neutral wire do

Answer 15

Blue
Completes the circuit and a current flows through it
It has around 0V

Question 16

What colour and what does the earth wire do

Answer 16

Green and yellow
For protecting the wiring and stops the appliance casing from becoming live

Question 17

What colour and what does the live wire do

Answer 17

Brown
Provides the alternating p.d (230v) from the mains supply

Question 18

What does the earth wire do if you touch the socket

Answer 18

Provide an alternative route and lower resistance path into the earth

Question 19

Equation for power

Answer 19

Power = E/t
Power = IV
Power = I^2R

Question 20

What is the national grid

Answer 20

A giant system of cables and transformers that covers the UK and connects power stations to consumers

Question 21

What does the national grid use in terms of p.d. and current

Answer 21

High p.d and low current
You’d lose loads of energy as the wires heat up
More efficient

Question 22

How are input power and output power linked in transformers

Answer 22

P1V1 = P2V2

Question 23

What happens when 2 insulating materials are rubbed together

Answer 23

Charged electrons will be scraped off one and dumped onto the other
This will leave the materials electrically charged - positive and negative

Question 24

What happens when an electric charge builds up on an object

Answer 24

The p.d between the object and the earth increases
If it increases to a large enough point then electrons can jump across the gap
They can also jump to any other earthed conductor