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GCSE Physics Paper 1 v2 > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is electrical current?

A

A flow of electrical charge. Current is never used up. The size of electrical current is the rate of flow of electrical charge

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2
Q

When will there be an electrical current?

A

When there is a closed circuit and a source of potential difference

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3
Q

What is the unit of current?

A

Ampere, A

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4
Q

What is the unit of potential difference?

A

Volt, V

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5
Q

What is potential difference?

A

It is the driving force that pushes the charge round. 1 volt tells us that 1 joule of energy is transferred for each coulomb of charge that is moving throughout the circuit.

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6
Q

What is resistance?

A

Anything that limits current

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7
Q

What is the unit of resistance?

A

ohm, Ω

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8
Q

What does an components current rely on?

A

The potential difference across it and the resistance of the component

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9
Q

How do you calculate current?

A 
It is the rate of flow of charge.
I=Q/t
I=V/R
I=P/V
P=I^2*R
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10
Q

What is a series circuit?

A

A circuit where the current can only flow in one path with no branches of wires. Within a series circuit the current is the same all around.

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11
Q

Which way does current flow from the battery or cell?

A

From the negative end to the positive

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12
Q

What measures current?

A

Ammeter

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13
Q

Which way is current drawn on a diagram?

A

From the positive end of the battery to the negative this is called the conventional current - opposite way that the current actually flows.

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14
Q

What is a parallel circuit?

A

It is a circuit that contains branches which splits current.. the current split between branches always adds up to the current leaving the cell this is because current is never used up in a circuit.

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15
Q

What store of energy does a cell have?

A

Chemical which transfers to electrical energy which is carried by electrons out of the cell.

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16
Q

What happens to potential difference when in a series circuit?

A

Potential difference is split up/shared and used by each component it flows through.

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17
Q

What happens to potential difference within a parallel circuit?

A

The potential difference across each individual component connected in parallel will stay the same.

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18
Q

How do you calculate the potential difference given out by batteries?

A

Add up the potential difference of the two cells.

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19
Q

How would wrongly arranging the cells in a battery effect the potential difference?

A

There would be no p.d. 0V. If a cell is pointing the wrong direction minus the voltage of that cell from the total voltage of all the cells added together.

20
Q

How is electrical charged measured?

A

In coulombs. 1 ampere=1 coulomb of charge flowing per second

21
Q

How do you calculate charge?

A

Q=I*t

22
Q

How do you work out energy transfer?

A

E=Q*V

E=Pt

23
Q

How does a component transfer energy?

A

In a metal wire electrons collide with metal atoms therefore some energy is transferred to thermal. The resistance tells us the p.d. required to drive a current though a component. Components with a higher resistance need more energy to drive the current therefore they output more energy.

24
Q

How do you work out resistance?

A

R=V/I

25
Q

How can you investigate factors affecting resistance?

A

Attach a crocodile clip to the wire level with 0cm on the ruler, attach the second clip 10cm away.
Close the switch then record the current through the wire and the p.d across it.
Then move the second clip further away and measure your results. Repeat this. You calculate the resistance of each length of wire by using the equation R=V/I

26
Q

What is an LDR?

A

It is a resister that changes resistance depending on the light intensity.

27
Q

What is a thermistor?

A

A resister dependant on temperature

28
Q

What happens to two resistors connected in parallel?

A

Their total resistance will be less than the smallest resistor. That is because both resistors have the same potential difference. By adding another loop the current has more than one direction to go.

29
Q

What is AC?

A

Alternating current. This is where the current is constantly changing direction this is produced by alternating voltage in which the positive and negative ends keep alternating. The UK mains uses AC the frequency of AC is 50 cycles per second or 50Hz

30
Q

What is DC?

A

Direct current, it is used within cells and batteries it is something that is always flowing in the same direction.

31
Q

What are the three wires most cables include?

A

Neutral,Live,Earth

32
Q

What does the neutral wire do?

A

It is a blue wire that completes the circuit and carries current away it is around 0V

33
Q

What does the live wire do?

A

It is a brown wire which provides the alternating p.d from the mains supply.

34
Q

What does the earth wire do?

A

It is a green and yellow wire that protects the wiring and for safety it prevents that appliances casing from becoming live. It doesn’t usually carry a current only when there is a fault. It is also at 0V.

35
Q

How can you get an electric shock?

A

If you touch a live wire because your body is at 0V a large potential difference is produced and current will flow through you. This then causes an electric shock.

36
Q

What will happen if the earth and live wire make a connection?

A

There will be a huge current flow with little resistance so a fire would start.

37
Q

What is an ohmic conductor?

A

It is a component where resistance does not change and it stays constant. However the resistance only stays constant if the temperature stays constant. The current through the resistor is directly proportional to p.p.

38
Q

What does filament mean?

A

A very thin wire these are used within filament lamps.

39
Q

Why is a filament lamp not an ohmic conductor?

A

The current that flows through the component is not directly proportional to the p.d. That is because the filament gets hot which increases the resistance at high temperatures the atoms in the filament vibrate more therefore the electrons in the current now collide more with the atoms so more energy is needed to push the current through the filament. At a certain point the current becomes the limiting factor.

40
Q

What is the national grid?

A

The national grid is a giant system of cables and transformers that covers the UK and connects power stations to consumers.

41
Q

Why does the national grid use high p.d and low current?

A

To transmit the huge amount of power you need either a high p.d or high current, the problem with a high current means that you lose a lot of energy through dissipation of thermal energy. This makes it efficient.

42
Q

How do you change the p.d within the grid to suit homes or transmissions?

A

Transformers are used:
Step-up transformer - this is where the p.d is increased for transporting.
Step-down - This is where p.d is reduced for domestic use.

43
Q

How do you cause static electricity?

A

When certain insulating materials are rubbed together negatively charged electrons will be scraped off one and passed to the other. This will leave the materials electrically charged with one positively charged and one negatively charged.

44
Q

How is a spark produced when dealing with static electricity?

A

AS an electric charge builds on an object the p.d between the object and earth (0V) will increase. If this gap gets large enough electrons can jump across the gap to the earth this produces a spark.

45
Q

What is an electric field?

A

An electric field is created around any electrically charged object. The closer you are the stronger the field is. You can show electric fields around an object using field lines. A charged object feels force within the field either attraction or repulsion.

46
Q

How do you draw an electric field?

A

You use field lines each line goes from positive to negative they are always at a right angle to the surface.

47
Q

How can you explain sparks in terms of an electrical field?

A

When there is a high p.d it cause a strong electrical field between the charged object and the earthed object. A strong electric field causes electrons in the air particles to be removed. Air is normally an insulator but when it is ionised it is much more conductive, so a current can flow through it this is a spark.

GCSE Physics Paper 1 v2 (5 decks)

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