Section 5 - Electricity

Question 1

What is a magnet?

Answer 1

Any material or object that produces a magnetic field

Question 2

What direction do magnetic field lines go?

Answer 2

From north to south

Question 3

What is induced magnetism?

Answer 3

A temporary magnetic field on a magnetic material that has been induced by a permanent magnet

Question 4

What is a magnetic material?

Answer 4

Am object that can be influenced by magnetic fields and has the potential to become a magnet

Question 5

What are some magnetic materials?

Answer 5

Nickel
Cobalt
Iron

Question 6

What is the difference between magnetically soft and hard materials?

Answer 6

Magnetically soft materials lose their magnetism quicker

Question 7

What is a battery?

Answer 7

Made up of two or more cells

Question 8

What is current?

Answer 8

Current is the rate of flow of charge measured in amps

Question 9

What is current measured by?

Answer 9

An ammeter

Question 10

What is emf?

Answer 10

The electromotive force is a measure of the electric work done moving each unit of charge round a circuit

Question 11

What is pd?

Answer 11

Potential difference is the amount of work done by each unit of charge as it passes through a component

Question 12

What is the formula for pd or emf?

Answer 12

Emf or pd = work/charge

Question 13

What is the formula for current?

Answer 13

Current = charge / time or I = Q/t

Question 14

What way round does the current flow in a circuit?

Answer 14

The positive terminal is the longer line of a cell, current flows from the negative to positive terminal.
Although conceptual current is positive to negative

Question 15

What is resistance?

Answer 15

Resistance is anything in the circuit which slows the flow of charge

Question 16

What is the equation for resistance?

Answer 16

Resistance = voltage / current Or V = IR

Question 17

What is the relationship between resistance and the length or cross sectional area of a wire?

Answer 17

Resistance is directly proportionate to is length
Resistance is inversely proportionate to its cross sectional area

Question 18

How does resistance change in a LDR?

Answer 18

As light gets brighter resistance falls, useful in automatic night lights

Question 19

How does resistance change in a thermistor?

Answer 19

As it gets hotter resistance drops, useful in car engineer

Question 20

What does a current-voltage graph show?

Answer 20

How current changes as potential difference is changed

Question 21

Describe the current-voltage graph of a resistor of constant resistance.

Answer 21

The graph is a straight line through the origin as current is directly proportionate to potential difference - ohms law

Question 22

What is ohms law?

Answer 22

Ohms law states that current is directly proportionate to potential difference in a fixed resistance resistor when external factors are constant

Question 23

Describe the current-voltage graph of a filament bulb.

Answer 23

Resistance resistance as current increases because as current increases, temp increases which causes more collisions with the electrons and ions. This increases resistance

Question 24

Describe the current-voltage graph of a diode.

Answer 24

Diodes only let current though in one direction. They have very high resistance in the reverse direction. So current is zero when pd is negative

Question 25

What is the formula for electric power and energy transferred?

Answer 25

Electric power (W) = current x potential difference Energy = current x potential difference x time

Question 26

Describe current in a series and parallel circuit?

Answer 26

Series - same Parallel - add to main

Question 27

Describe pd in series and parallel circuits?

Answer 27

Series - adds Parallel - same

Question 28

How to calculate total resistance in parallel?

Answer 28

1/Rt = 1/R1 + 1/R2 + 1/R3

Question 29

Explain resistance in series and parallel.

Answer 29

Series - add up/ sum of Parallel - weird calculation

Question 30

How can you test electric conductors or insulators?

Answer 30

Place in a circuit with a filament lamp

Question 31

What is an electric field?

Answer 31

An electrified is an area where a force acts on a electric charge

Question 32

What are the three types of wires in a uk plug?

Answer 32

Live Neutral Earth

Question 33

What can a sudden increase in current or surge or overloading do?

Answer 33

Damage the appliance Cause fires of electric shocks

Question 34

What can damp controls do to an electrical circuit?

Answer 34

Can cause electric shock as impure water can conduct electricity

Question 35

What can overheating cables do to an electrical circuit?

Answer 35

Causes a fire

Question 36

What can damaged wire insulation do to a circuit?

Answer 36

Lead to live wire being exposed. Could cause shock

Question 37

What is the usual voltage from a ac supply?

Answer 37

230V

Question 38

What is the use of a fuse and why do they come in different ratings?

Answer 38

Contains a thin piece of wire that melts when the current gets too high to break the circuit. Different ratings are used depending on what current you want to break the circuit.

Question 39

What is a circuit breaker?

Answer 39

Circuit breakers or trip switches are similar to fuses in that break the circuit, They do this by opening or tripping which means they don’t need to be replaced every time they trip

Question 40

What is the importance of double casing or earthing?

Answer 40

When a surge causes a wire to touch a metal case it may cause a shock. Double casing or earthing prevents this

Question 41

What is double casing?

Answer 41

Double casing is a plastic casing that goes over an Epstein appliance to stop electric shocks. Appliances that are double cased do not need an earth wire.