# Physics - P5

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• Created by: L_Georgie
• Created on: 16-04-16 13:16
What happens when you rub two insulating materials together?
Electrons are scrapped off one and on to the other meaning that one material will be positively charged and the other negatively.
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What happens to two things that have opposite electric charges?
They are attracted to each other.
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What happens to two things that have the same electronic charge?
They will repel each other.
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Why do you often find dust on lots of surfaces in a house?
Because the dust particles in the air are very easily attracted to anything that is charged.
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What is an electric current?
The flow of charge around a circuit.
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Why does a current flow in a metal conductor but not a insulator?
Because in a metal the electrons are free to move around and in insulators the elctrons can't move.
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What does a battery do in a complete circuit?
The battery pushes the free charges through the wires and around the circuit.
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What do the voltage of a circuit mean?
The voltage is the driving force that pushes the current around the circuit.
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What happens to the current if there is no voltage?
If there is no voltage then the current can't flow.
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What happens to the current if you increase the resistance in a circuit?
The less current will flow through the circuit.
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What is power?
The rate at which an electrical power supply transfers energy to an appliance.
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Where would you place an ammeter in a circuit? (parallel or series)
Series.
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Where would you place a voltmeter in a circuit? (parallel or series)
Parallel, around the component under test.
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What does potential difference show us?
How much energy is transferred between to or from each unit of charge as it moves between two points.
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Why must a voltmeter be placed parallel in a circuit?
So it can compare the energy a charge has before and after passing through a component.
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What is the current through a component proportional to?
The voltage across it when it stays constant.
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Why do resistors get hot when a current passes through them?
When electrons move through a resistor, they collide with positive ions in the resistor which causes the ions to vibrate more.
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What does a thermistors resistance depend on?
The temperature.
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How many volts is the UK mains electricity supply, is it AC or DC?
230V and it's AC
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What does AC stand for and what does it mean?
AC = Alternating Current. It means that the current is constantly changing direction.
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What does DC stand fro and what does it mean?
DC = Direct Current. It means that the current always flows in the same direction.
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How can you create a voltage in a conductor?
By moving a magnet in or near a coil of wire.
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How does moving a magnet near a coil of wire induce a voltage?
As you move the magnet the magnetic field through the coil changes this change induces a voltage across the end of the ends of a coil.
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How could you increase the voltage induced in a generator?
You could add an iron core inside of the coil, increase the strength of the magnetic field, increase the speed of rotation or increase the number of turns on the coil.
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What are transformers used for?
Transformers are used to change the size of a voltage.
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What does a step-up transformers do?
They increase the voltage of something by having more turns on the secondary coil than the primary coil.
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What does a step-down transformer do?
They decrease the voltage of something by having more turns on the primary coil than the secondary coil.
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How do transformers actually work?
The primary coil produces a magnetic field that stays in the iron core, this is an AC current so the magnetic field in the iron core changes direction constantly this changing direction induces a voltage in the secondary coil.
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What happens if you supply a DC current to the primary coil?
You would get nothing out of the secondary coil because the magnetic field in the iron core wouldn't be changing.
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What is a magnetic field?
A region where magnetic materials and also wires carrying currents experience a force acting on them.
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What is a uniform magnetic field?
A magnetic field that has the same strength everywhere in the field.
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What happens if a regular coil of wire carrying a current is placed in a uniform magnetic field?
The force will cause the wire to turn.
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What does a split-ring communicator do?
It swaps the contacts every half turn which allows the coil to keep rotating continuously in the same direction.
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What happens if the spilt-ring communicator wasn't there?
The direction of the force would reverse every half turn and so the coil would change direction every half turn.
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## Other cards in this set

### Card 2

#### Front

What happens to two things that have opposite electric charges?

#### Back

They are attracted to each other.

### Card 3

#### Front

What happens to two things that have the same electronic charge?

### Card 4

#### Front

Why do you often find dust on lots of surfaces in a house?

### Card 5

#### Front

What is an electric current?