Electricity

Question 1

What is the resistance of a ohmic conductor

Answer 1

The resistance doesn’t change with the current,the current flowing is directly proportional to the potentials differnce

Question 2

What resistors change resistance

Answer 2

Diode and filament lamp

Question 3

What does a filament lamp do

Answer 3

When an electrical charge flows though it transfers energy to the thermal energy store of the filament.Resistance increases as temp does

Question 4

What’s is a diodes resistance

Answer 4

One way it will let currents through however the other way the resistance will be very high

Question 5

What does the ammeter do and how should it be placed

Answer 5

Measures currents (A)
The ammeter must be placed in a series with what your testing

Question 6

What is the voltmeter

Answer 6

It measures potential difference
It must always be placed in parallel with the thing your testing

Question 7

What should the IV characteristics of a ohmic conductor,fillament lamp and slide look like

Answer 7

Ohmic conductor:diagonal straight line
Filament lamp:a curve like a stretched S
Diode:A steep curved line on only +axis

Question 8

What is an IV characteristic

Answer 8

Refers to graph which shows current flowing through a component changes as potential difference across has changes

Question 9

What is an LDR

Answer 9

A resister that is dependent on light
When bright resistance is low
When dark resistance is highest

Question 10

What is a thermistor

Answer 10

A temp dependent resistor
When cooler the resistance goes up
When hotter the resistance drops

Question 11

How can you use a thermistor in a sensing circuit

Answer 11

Fan in a room
As the room gets hotter thermistor resistance decreases and takes a smaller share of potencies difference from power supply
Potwnical differnce across fixed resistor and fan rises ,making fan go faster

Question 12

What do cell potenical differences do

Answer 12

They add up provided cells are connected same way

Question 13

In a parallel circuit the potential differnce is what

Answer 13

The same across all components

Question 14

In a parallel circuit the current is what

Answer 14

Shared across branches

Question 15

In a series circuit what does resistance do

Answer 15

Add up

Question 16

In a parallel circuit what does resistance do

Answer 16

Reduce the total resistance

Question 17

Why are series circuits not widely used

Answer 17

Due to if one component it’s removed the whole circuit will not work

Question 18

In a seriers circuit the potential differnce is

Answer 18

Shared across all components

Question 19

The current In a series circuit is what

Answer 19

The same everywhere

Question 20

What does ac and dc mean

Answer 20

Alternating current and direct current

Question 21

What current does the Uk mains supply use and what voltage is it at

Answer 21

Uk uses AC at around 230V

Question 22

What are the 3 wires found in cables

Answer 22

Neutral wire,earth wire and live wire

Question 23

What is the neutral wire

Answer 23

The neutral wire completes the circuit it’s around 0V

Question 24

What is the live wire

Answer 24

The live wire provides the alternating potential difference at 230v

Question 25

What is the earth wire

Answer 25

It’s for protecting the wiring and for safety it stops the appliance casing from becoming live
It dosnt shaky carry a current,only when there’s a fault
Also 0V

Question 26

What’s the problem with touching a live wire

Answer 26

Like the earth you body is 0V this means by touching a live wire a large potential difference is produced across your body and current flows through you and causes and electric shock

Question 27

If you touch a turned off light switch how can you still get shocked

Answer 27

Current isn’t flowing however there is still a a potenical difference in the live wire

Question 28

Why is a connection between the live wire and earth dangerous

Answer 28

Due to their being a low resistance path to earth meaning a huge current will flow

Question 29

What is the national grid

Answer 29

A giant system of cables and transformers that cover the Uk and connects power stations to consumers

Question 30

How does daytime affect every usage

Answer 30

Throughout the day energy demand changes

Question 31

What events can affect energy use age

Answer 31

When people wake up ,coming home from work and school and popular events

Question 32

Why do power stations run below their maximum power output

Answer 32

So there’s capacity to cope with high demand

Question 33

What’s the practical for IV charectoristics

Answer 33

1)set up test circuit
2)beguin to vary variable resister.This will variate the Current flowing and the potential difference across the component
3)take several pairs of readings from ammeter and voltmeter to see how potential difference across the component changes
4)repeat each reading twice to get Adverage potential difference
5)swap over wires connnected so the direction of current is reversed
6) plot a graph of current agains voltage

Question 34

What does direct potential current mean

Answer 34

The polarity does not change

Question 35

How does adding resisters to a series graph change it

Answer 35

It increases the total resistance of the circuit and decreases the total current
Leading a to a graph that appears is straight and diagonal

Question 36

If a switch was placed incorrectly on a circuit how would that affect the current in the variable resistor

Answer 36

The current would be almost zero due to the switch having basically no resistance

Question 37

Name the type of relationship between current and potential difference for a resistor at
constant temperature.

Answer 37

Ohms law

Question 38

Explain the difference between direct and alternating potential difference.

Answer 38

An alternating potential difference will lead to an alternating current, whilst a direct potential difference leads to a direct current

Question 39

What do resisters in parallel do

Answer 39

Always less than the lowest resister