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Physics 1 > Electricity > Flashcards

Electricity Flashcards

1
Q

What quantity does the ammeter measure?

A

Current

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2
Q

What is 1mA in amps?

A

0.001 amps (divide by a 1000 as milli is a thousandth)

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3
Q

Explain how components should be connected so total resistance is as low as possible.

A

In parallel so the current has multiple pathways to take (resistance is smaller than the smallest individual resistor)

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4
Q

How do you identify a relationship as inversely proportional?

A

The product of the two variables is constant.

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5
Q

Explain what happens to a filament bulb as pd increases.

A

Current increases so temperature of the filament increases. Therefore, resistance increases.

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6
Q

Describe the type of forces between static hair and a balloon.

A

Non contact electrostatic forces. There is attraction between the hair and balloon as they are oppositely charged

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7
Q

Explain why a plug needs a live and neutral wire.

A

-Live wire carries the potential difference (230V)
-Neutral wire completes the circuit

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8
Q

Suggest why houses are supplied with dangerous mains electricity.

A

Appliances need a high power supply for domestic use
Earth wires are put in place as safety to prevent dangers

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9
Q

Explain why when a student rubs a cloth and a plastic rod the rod becomes positively charged.

A

Friction caused. Negatively charged electrons are transferred from the rod to the cloth. The rod loses negative electrons so has an overall positive charge as more positive charges than negative charges.

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10
Q

Explain why a mass may increase when two rods are put together and do not touch.

A

An additional force increases mass. This force is caused as both rods have the same charge and like charges repel (non contact force).

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11
Q

Explain why a man can still get an electric shock from a wire if the switch is open.

A

One of the wires is live (carries a pd of 230V). As the man is earthed (0V) a large pd exists between the man and the wire. Therefore, charge will try and flow through the man to be earthed causing an electric shock.

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12
Q

Explain why a step down transformer is used.

A

Decreases pd so current increases to a safe measure for domestic use.

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13
Q

Give examples of a direct current.

A
  • Battery
  • Cell
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14
Q

Give examples of an alternating current.

A

The National Grid/Mains electricity

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15
Q

RPA 4: how would you use equipment to investigate how the current affects a component?

A
  • Close switch and switch on power supply
  • Use ammeter to record the current
  • Use voltmeter to record potential difference
  • Use a variable resistor to alter the current and take further readings
  • Reverse the current by swapping the wires around to take a range of (negative) readings of current and potential difference
  • Repeat to calculate a mean of each point
  • Plot a graph of V against I (IV graph) to show their relationship
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16
Q

Describe the action of the fuse in a circuit

A

If current above the value of the fuse the wire in the fuse melts and so the circuit breaks.

17
Q

What determines an ohmic conductor?

A

Current and potential difference are directly proportional so resistance and temperature are constant.

18
Q

Why should an ammeter have a low resistance?

A

To affect current as little as possible (if resistance was too high it would lower current)

19
Q

How can an electric shock be caused when a person touches a live wire.

A

Live wire has a pd of 230V person has a pd of 0V so a large pd exists between them so charge will want to flow through the person to be earthed.

20
Q

Explain why reducing energy used of an appliance could reduce the amount of carbon dioxide emitted into the atmosphere and the effect on the environment.

A

Less fossil fuels are burned as less electricity is needed/used so less global warming as CO2 contributes to it.

21
Q

Explain why the student should open the switch after each reading

A

The wire and so the resistor would get hot and could overheat. Resistance would increase.

22
Q

Why would you not become electrically charged if an object is a metal?

A

Metal is a conductor so there wouldn’t be a build up of charge as it would pass through metal (and be earthed)as electrons can flow

23
Q

Why does a negatively charged person receive an electric shock when touching a metal?

A

(Large) potential difference exists between them so negatively charged electrons transfer from the charged person to the metal which earths the charge

24
Q

Why is it dangerous for a live wire to touch a metal casing?

A

Casing will become live so a risk of electric shock

25
Q

What is a zero error with an ammeter?

A

When the ammeter displays a reading that is not 0 when it is not connected

26
Q

Why when cells are put the wrong way around in an LED circuit does the torch not work?

A

LED is a diode so current only flows in one direction whereas there is very high resistance in the opposite direction

27
Q

Explain the purpose of the step up transformer.

A

Increases potential difference which decreases current. Less thermal energy is lost to the surroundings from the transmission cables which increases efficiency of national grid.

28
Q

Explain the purpose of a step down transformer

A

Decreases potential difference (increasing current) to a safe value for domestic use

29
Q

What happens to power output in a parallel circuit if more switches are turned on?

A

Resistance decreases so current increases meaning power output increases (at a fixed voltage)

30
Q

Why is it not correct to say as potential difference is doubled power output increases?

A

As potential difference increases resistance increases so current decreases. This means current and potential difference are not directly proportional.

31
Q

Define an electric field

A

Produced around all charged objects - a non contact force is experienced in this region when interacts with charged particles

32
Q

Define static electricity and how it is caused

A

Non contact force that acts on charged particles in a field

33
Q

What can a strongly charged object result in and why?

A

Has a strong electric field which can ionise the air (ionisation). This means air loses some of its electrons and can conduct electricity, so charge can travel through air causing static electricity.

33
Q

Define a power rating

A

Rate energy is transferred

34
Q

What do arrows on an electric field show?

A

Way a positive charge would be pushed

Physics 1 (4 decks)

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