Section 5 - Electricity Flashcards

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1
Q

What is a magnet?

A

Any material or object that produces a magnetic field

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2
Q

What direction do magnetic field lines go?

A

From north to south

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3
Q

What is induced magnetism?

A

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

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4
Q

What is a magnetic material?

A

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

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5
Q

What are some magnetic materials?

A

Nickel
Cobalt
Iron

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6
Q

What is the difference between magnetically soft and hard materials?

A

Magnetically soft materials lose their magnetism quicker

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7
Q

What is a battery?

A

Made up of two or more cells

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8
Q

What is current?

A

Current is the rate of flow of charge measured in amps

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9
Q

What is current measured by?

A

An ammeter

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10
Q

What is emf?

A

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

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11
Q

What is pd?

A

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

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12
Q

What is the formula for pd or emf?

A

Emf or pd = work/charge

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13
Q

What is the formula for current?

A

Current = charge / time or I = Q/t

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14
Q

What way round does the current flow in a circuit?

A

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

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15
Q

What is resistance?

A

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

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16
Q

What is the equation for resistance?

A

Resistance = voltage / current Or V = IR

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17
Q

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

A

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

18
Q

How does resistance change in a LDR?

A

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

19
Q

How does resistance change in a thermistor?

A

As it gets hotter resistance drops, useful in car engineer

20
Q

What does a current-voltage graph show?

A

How current changes as potential difference is changed

21
Q

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

A

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

22
Q

What is ohms law?

A

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

23
Q

Describe the current-voltage graph of a filament bulb.

A

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

24
Q

Describe the current-voltage graph of a diode.

A

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

25
Q

What is the formula for electric power and energy transferred?

A

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

26
Q

Describe current in a series and parallel circuit?

A

Series - same
Parallel - add to main

27
Q

Describe pd in series and parallel circuits?

A

Series - adds
Parallel - same

28
Q

How to calculate total resistance in parallel?

A

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

29
Q

Explain resistance in series and parallel.

A

Series - add up/ sum of
Parallel - weird calculation

30
Q

How can you test electric conductors or insulators?

A

Place in a circuit with a filament lamp

31
Q

What is an electric field?

A

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

32
Q

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

A

Live
Neutral
Earth

33
Q

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

A

Damage the appliance
Cause fires of electric shocks

34
Q

What can damp controls do to an electrical circuit?

A

Can cause electric shock as impure water can conduct electricity

35
Q

What can overheating cables do to an electrical circuit?

A

Causes a fire

36
Q

What can damaged wire insulation do to a circuit?

A

Lead to live wire being exposed. Could cause shock

37
Q

What is the usual voltage from a ac supply?

A

230V

38
Q

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

A

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.

39
Q

What is a circuit breaker?

A

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

40
Q

What is the importance of double casing or earthing?

A

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

41
Q

What is double casing?

A

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.