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Physics > Mains electricity > Flashcards

Mains electricity Flashcards

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1
Q

How does the use of insulation protects a device?

A

To prevent electric shocks

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2
Q

What is double insulation?

A

The appliance has insulation around both casing and around the cables.

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3
Q

What is earthing?

A

Provides a path for a conductor pathway for excess charges to flow safely away to the ground.

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4
Q

Explain how a fuse protects a circuit

A

If a dangerously large current starts to flow in a circuit, the fuse will overheat and melt, causing a break in the circuit.

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5
Q

What happens to the temperature of wire when a current is put through it?

A

The temperature increases

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6
Q

Equation for Power current and voltage is…

A

Power = current x voltage

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7
Q

What is the use of a circuit breaker?

A

They automatically switch off the circuit when they detect an overload or short circuit.

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8
Q

Current in a resistor

A

Causes electrical energy to be transferred as heat, increasing temperature. Used in devices like heaters and toasters.

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9
Q

Energy transfer formula

A

Energy transferred = current x voltage x time OR Energy transferred = charge x voltage

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10
Q

Alternating Current

A

This is current flowing in different directions continuously.

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11
Q

Direct Current

A

This is current flowing in the same direction.

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12
Q

Series Circuits

A

Components connected end-to-end, same current flows through all component.

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13
Q

Parallel circuits

A

Components connected across common points, each component gets the full voltage. Ideal for domestic lighting as each light operates independently.

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14
Q

Current in a series circuit

A

Current depends on the applied voltage and the total resistance.

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15
Q

Voltage in a parallel circuit

A

Voltage is the same across all branches, current divides among the branches.

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16
Q

Current and voltage are what?

A

Proportional to each other during fixed resistors

17
Q

What is ohm’s law and what follows it?

A

ohm’s law is that for a component at constant temperature, voltage is proportional to current. Resistors follow ohm’s law.

18
Q

Metal filament lamps

A

Don’t follow ohm’s law. Resistance increases with temperature.

19
Q

Diodes

A

Allow current to flow in one direction only.

20
Q

Explain why parallel circuits are more suitable for use in the home

A

As you can turn the lights on/off individually.

21
Q

Line going through graph for a resistor

A

Straight diagonal line

22
Q

Line going through for a filament lamp

A

Flat S shape but look at revision

23
Q

Line going through for a diode

A

Look at revision

24
Q

What is the definition of voltage

A

The energy transferred per unit of charge passed.

25
Q

What is the definition of volt

A

A joule per coulomb

26
Q

Why is current conserved at a junction in a circuit?

A

As charge can not be created or destroyed

27
Q

What is used to indicate the presence of current in a circuit?

A

LED’s and lamps

28
Q

Describe the qualitative effect of changing resistance on the current in a circuit

A

Increasing the current decreases resistance and decreasing the current increases the resistance

29
Q

Describe the qualitative variation of resistance of LDR’s with illumination and thermistors with temperature

A

The resistance of an LDR decreases with increasing illumination, while the resistance of a thermistor decreases with increasing temperature.

30
Q

Current definition

A

The rate of flow of charge

31
Q

What is electric current in solid metallic conductors?

A

A flow of negatively charged electrons

32
Q

What is the voltage across two components that are parallel to each other

A

The same

33
Q

How can insulating materials be charged by friction?

A

Rubbing transfers electrons from one material to the other, creating opposite charges

34
Q

Voltmeters - series or parallel

A

Parallel

35
Q

Ammeters - series or parallel

A

Series

36
Q

Uses of electrostatic charges

A

Photocopiers and inkjet printers

37
Q

Fuelling aircraft

A

As electrostatic charges may create sparks when refuelling so for safety that it needs to be earthed.

Physics (1 decks)

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