P3 - Electric circuits

Question 1

What is the motor effect

Answer 1

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

Question 2

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

Answer 2

90 degrees, to feel the full effect of the force

Question 3

What causes the force felt on a current carrying wire

Answer 3

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

Question 4

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

Answer 4

It will feel less force

Question 5

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

Answer 5

The direction of the magnetic field
The direction of the current

Question 6

What does fleming’s left hand rule tell you

Answer 6

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

Question 7

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

Answer 7

index finger (point from N to S)

Question 8

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

Answer 8

The direction of current along the wire

Question 9

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

Answer 9

The direction of the force felt by the wire

Question 10

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

Answer 10

F = BIL

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

Question 11

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

Answer 11

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

Question 12

How can you change the direction of current in a generator

Answer 12

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

Question 13

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

Answer 13

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

Question 14

Why do we need step up transformers

Answer 14

To minimise the energy loss over long distances

Question 15

Why do we need step down transformers

Answer 15

To make the voltage safe for everyday use

Question 16

What is the voltage in power cables

Answer 16

400,000 V

Question 17

What is the voltage in homes

Answer 17

230 V

Question 18

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

Answer 18

Primary coil, iron core, secondary core

Question 19

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

Answer 19

The secondary coil had twice as many coils

Question 20

What are the stages of a transforment

Answer 20

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

Question 21

What do transformers change

Answer 21

The voltage

Question 22

What is the equation for Voltage

Answer 22

V = IR

Question 23

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

Answer 23

It will decrease

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Why do diodes only work in one direction

Answer 26

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

Question 27

Why does adding resistors in parallel decrease the total resistance?

Answer 27

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

Question 28

Equation linking power, current resistance

Answer 28

P = I^2R

Question 29

In a series circuit, what happens to the voltage

Answer 29

The total voltage is shared by the individual components

Question 30

In a series circuit, what happens to the current

Answer 30

It is the same everywhere

Question 31

In a series circuit, what happens to the resistance

Answer 31

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

Question 32

Will components with a greater resistance have more or less voltage

Answer 32

More

Question 33

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

Answer 33

Point from north to south

Question 34

In a parallel circuit, what happens to the voltage

Answer 34

It is the same across all branches

Question 35

In a parallel circuit, what happens to the current

Answer 35

It is shared between the branches

Question 36

In a parallel circuit, what happens to the resistance

Answer 36

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

Question 37

What is the symbol for a fuse

Answer 37

A box with the wire running through the middle

Question 38

What is the symbol for a diode

Answer 38

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

Question 39

What is the symbol for a led

Answer 39

A diode with two lines coming off of it

Question 40

What is the symbol for a variable resistor

Answer 40

A resistor with a diagonal arrow running through

Question 41

What is the symbol for a light dependant resistor

Answer 41

A resistor in a circle with 2 arrows facing it

Question 42

What is the symbol for a thermistor

Answer 42

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

Question 43

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

Answer 43

It decreases

Question 44

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

Answer 44

It decreases