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GCSE Physics > P3 - Electric circuits > Flashcards

P3 - Electric circuits Flashcards

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1
Q

What is the motor effect

A

The idea that a current carrying wire in the the presence of a magnetic field will experience a force

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2
Q

What angle does the wire have to be to the direction of magnetic field

A

90 degrees, to feel the full effect of the force

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3
Q

What causes the force felt on a current carrying wire

A

The two magnetic fields interacting, pushing the wire out of the magnetic feild

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4
Q

What will happen to the wire if it is at an angle to the magnetic feild

A

It will feel less force

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5
Q

What do you need to know to find the direction of the force (motor effect)

A

The direction of the magnetic field
The direction of the current

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6
Q

What does fleming’s left hand rule tell you

A

The direction of force felt by a current carrying wire in a magnetic field

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7
Q

In fleming’s left hand rule, what do you match up with the direction of magnetic field

A

index finger (point from N to S)

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8
Q

In fleming’s left hand rule, what do you line up the middle finger with

A

The direction of current along the wire

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9
Q

What does the direction of the thumb tell you, in fleming’s left hand rule

A

The direction of the force felt by the wire

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10
Q

What is the formula for the size of the force felt by the current carrying wire

A

F = BIL

B = magnetic flux density
I = current
L = length of wire

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11
Q

How can you create a potential difference and current with a magnet and a wire

A

By moving either the wire, or the magnet through each other, a potential difference and current will be made

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12
Q

How can you change the direction of current in a generator

A

By changing the direction of the magnet (or wire), or changing the orientation of the magnet

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13
Q

What 3 ways can you increase the size of the potential difference and current made by a generator

A

Increase the strength of the magnet
Move the wire more quickly
Make more turns in the coil

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14
Q

Why do we need step up transformers

A

To minimise the energy loss over long distances

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15
Q

Why do we need step down transformers

A

To make the voltage safe for everyday use

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16
Q

What is the voltage in power cables

A

400,000 V

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17
Q

What is the voltage in homes

A

230 V

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18
Q

What is the first coil, the centre, and the second coil called

A

Primary coil, iron core, secondary core

19
Q

If 10 volts goes in and 20 comes out, what happened to the ratio

A

The secondary coil had twice as many coils

20
Q

What are the stages of a transforment

A

An alternating potential difference is applied across the primary coil
This causes an alternating current, which generates an alternating magnetic field which induces a field in the core
This induces a potential difference across the secondary wire, (because the magnetic field direction was alternating), and makes a current flow around the secondary coil

21
Q

What do transformers change

A

The voltage

22
Q

What is the equation for Voltage

A

V = IR

23
Q

If the voltage stays constant and the current increases, what will happen to the resistance

A

It will decrease

24
Q

On a VI graph, will a wire with more resistance make a steeper or shallower line

A

Shallower, because it requires more voltage to get a small current

25
Q

Why is the line of a filament lamp on a VI graph curved down

A

Because as the current increases, the filament gets red hot, which increases the resistance. This means that the currents rate of increase will slow as the voltage gets increased

26
Q

Why do diodes only work in one direction

A

Because there is a very high resistance in the reverse direction, meaning no current can flow

27
Q

Why does adding resistors in parallel decrease the total resistance?

A

There are more routes for electrons to take between the branches, so it is easier for current to flow.

28
Q

Equation linking power, current resistance

A

P = I^2R

29
Q

In a series circuit, what happens to the voltage

A

The total voltage is shared by the individual components

30
Q

In a series circuit, what happens to the current

A

It is the same everywhere

31
Q

In a series circuit, what happens to the resistance

A

The total resistance is the sum of the resistance felt by all the components

32
Q

Will components with a greater resistance have more or less voltage

A

More

33
Q

In fleming’s left hand rule, which pole do u point at

A

Point from north to south

34
Q

In a parallel circuit, what happens to the voltage

A

It is the same across all branches

35
Q

In a parallel circuit, what happens to the current

A

It is shared between the branches

36
Q

In a parallel circuit, what happens to the resistance

A

The more loops in the circuit, the less overall resistance there is

37
Q

What is the symbol for a fuse

A

A box with the wire running through the middle

38
Q

What is the symbol for a diode

A

A circle, with a right facing triangle and line, with the wire running through the middle

39
Q

What is the symbol for a led

A

A diode with two lines coming off of it

40
Q

What is the symbol for a variable resistor

A

A resistor with a diagonal arrow running through

41
Q

What is the symbol for a light dependant resistor

A

A resistor in a circle with 2 arrows facing it

42
Q

What is the symbol for a thermistor

A

A resistor with a diagonal line running through with a little flat bit at the end

43
Q

As light gets more, what happens to the resistance in a light dependant resistor

A

It decreases

44
Q

As heat gets more, what happens to the resistance in a thermistor

A

It decreases

GCSE Physics (8 decks)

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