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Physics > Electricity and circuits T5 > Flashcards

Electricity and circuits T5 Flashcards

1
Q

What is current?

A

The flow of electric charge around a circuit. Unit : ampere

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2
Q

What is the potential difference?

A

The potential difference (or voltage) is the driving force that pushes the charge around. Unit : volt. The potential difference is the energy transferred per coulomb of charge

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3
Q

What is resistance?

A

Resistance is anything that slows the flow down. Unit : ohm

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4
Q

What happens when there is a high potential difference?

A

There is a high current

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5
Q

What will happen if there is a high resistance?

A

There will be a low current

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6
Q

How do you work out charge?

A

Charge = current x time

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7
Q

What unit is charge in?

A

Coulombs

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8
Q

How do you work out energy transferred?

A

Energy transferred = charge moved x potential difference

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9
Q

How to work out resistance?

A

Resistance = potential difference / current

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10
Q

What does an ammeter do?

A

This measures the current (in amps) flowing through the component. It can be put anywhere in the main circuit

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11
Q

What does a volt meter do?

A

This measures the potential difference across the component. It must be placed under parallel with the component under test

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12
Q

What do linear components have on an iv graph?

A

A straight line

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13
Q

What do non - linear components have on an iv graph?

A

A curved line

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14
Q

How to work out the resistance on an iv graph?

A

The resistance will be the inverse of the gradient or 1/gradient. The steeper the graph the lower the resistance

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15
Q

What is an ldr?

A

An ldr ( light dependent resistor) is a resistor that is dependent on the intensity of light. In bright light, resistance falls. In darkness, the resistance is highest

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16
Q

What is a thermistor?

A

A thermistor is a temperature dependent resistor. In hot conditions, the resistance drops. In cool conditions, the resistance goes up

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17
Q

Which way do electric field lines travel?

A

Positive to negative

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18
Q

Which way do electric filed lines face?

A

At a right angle to the surface

19
Q

What do close filed lines represent?

A

A stronger electric field

20
Q

How do photocopiers work?

A

They use static electricity the copy images onto a charged plate before printing them

21
Q

How do electrostatic sprayers work?

A

Bikes and cars are painted using electrostatic paint sprayers. The spray gun is charged, which charges up small drops of paint, each drop repels all others, so you get a very fine, even layer of paint over the the bike or car

22
Q

How can static electricity be dangerous when refuelling a car?

A

A fuel flows out of a fuelling pipe, eg a aircraft or tanker, then static electricity can build up, this can easily cause a spark which can lead to an explosion

23
Q

What happens when electric charge builds up on an object?

A

The potential difference between the object and the earth increases, if the potential difference gets large enough, electrons can jump across the gap between the charged object and the earth

24
Q

What happens with 2 things with opposite electric charges?

A

They are attracted to each other

25
Q

What happens to 2 electric things with the same charge?

A

The repel each other

26
Q

What happens with insulating materials are rubbed toegther?

A

Negatively charged electrons will be scraped off one and dumped on the other, as the materials are insulators, these electrons are not free to move, this build up of charge is static electricity

27
Q

What is a series circuit?

A

In a series circuit, the different components are connected in a line, end to end. If you disconnect 1 component, the circuit is broken

28
Q

What is a parallel circuit?

A

In parallel circuits, each component is separately connected to the power, if you move or disconnect one of them it will hardly change the others at all

29
Q

What happens to the p.d. And the current in a series circuit?

A

Theres a bigger p.d when there are more cells in a series, e.g 2 batteries with 1.5 v supply 3 v. The current is equal everywhere I1 = I2 = I3

30
Q

What happens to the p.d and the current in a parallel circuit?

A

In a parallel circuit, the potential difference is the same across all components v1 = v2 = v3. Current is shared between branches. The total current flowing around the circuit is equal to the total of all the currents through the separate components. Itotal = i1 + i2

31
Q

What happens when you add a resistor in a series circuit?

A

The total resistance increases because by adding a resistor, the two resistors share the total p.d

32
Q

What happens when you add a resistor to a parallel circuit?

A

The total resistance decreases because, if you have 2 resistors in parallel, their total resistance is less than the resistance of the smallest of the 2 resistors

33
Q

How do you work out energy transferred?

A

Energy transferred = current x p.d x time

34
Q

How is energy transferred in a kettle?

A

The energy is electric which then transfers to the thermal energy of the kettle

35
Q

How do you work out power?

A

Power (w) = energy transferred / time

36
Q

How do you work out electrical power?

A

Electrical power = current x p.d

37
Q

What is an a.c?

A

In a.c supplies the movement of the charges is constantly changing direction. Alternating currents are produced by alternating voltages

38
Q

What is a d.c?

A

In direct current the movement of the charges is only in 1 direction. Its created by a direct voltage

39
Q

What is the live wire?

A

Brown, the live wire carries the voltage. Goes up to 230 v

40
Q

What is the neutral wire?

A

Blue the neutral wire completes the circuit, electricity normally flows in through the live and out through the neutral wire. The neutral wire is always at 0v

41
Q

What is the earth wire?

A

Green and yellow, the earth wire is for safety and protecting the wiring. It carries the current away if something goes wrong and stops the appliance casing going live. Its also at 0v

42
Q

What is an electric shock?

A

Your body is at 0v, this means that if you touch the live wire, a potential difference is produced across your body and a current flows through you. This causes a large electric shock which could kill you

43
Q

How does a fuse work?

A

When a voltage gets too high, the fuse wire melts so that no more electricity can come through

44
Q

What is a circuit breaker?

A

Instead of a fuse wire, the circuit breaker may just trip something to the power of. Circuit breakers turn off quicker than fuses do and can be reset, but are more expensive

Physics (5 decks)

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