E.I.N.T.K

Question 1

define electrical field

Answer 1

it is a region where a charge that experiences a force

Question 2

define magnetic field

Answer 2

The region around a magnet where a force acts on another magnet or on a magnetic material

it is a region around a magnet where another magnet experiences a force

Question 3

describe an electric field around a point charge

Answer 3

positive point charge: arrows go away from the atom

negative point: arrows go towards the atom

Question 4

which direction does current flow in, in an electric field

Answer 4

arrows go from north to south, left to right if vertical

Question 5

describe how to charge a body by static electricity

Answer 5

1. start off by having a neutral body
2. bring a positively charged rod towards the body (all electrons will move to the side with the rod)
3. connect the body to earthing (this will bring in more electrons)
4. remove earthing first to be stuck with a negative charge
5. remove rod last
   the above is to negatively charge a neutral body so do the opposite to positively charge a neutral body

• *in step 2 use a -ve charged rod
• *in step 3 when earthing is connected electrons flow into the earth

Question 6

describe 3 methods of magnetising

Answer 6

1. stroking method - stroke a ferrous unmagnetised material with a north pole of a strong magnet and repeat many times
2. electrical method - wind a wire round a ferrous material and run a direct current through it

Question 7

methods of demagnetisation

Answer 7

1. hammering
2. hit
3. using an alternating current

Question 8

same currents…

Answer 8

attract

Question 9

opposite currents…

Answer 9

repel

Question 10

what is a galvanometer

Answer 10

it is a sensitive ammeter

Question 11

describe what happens when a magnet passes through a galvanometer

Answer 11

1. deflection then reverse deflection
   (when a north pole passes through)
2. deflection is larger
   (when a south pole passes through first)
3. as the magnet moves the coil cuts the magnetic field lines inducing an EMF

Question 12

ways to increase induced EMF

Answer 12

1. move the magnet faster - faster speed
2. put more turns on the coil
3. use a stronger magnet

Question 13

describe features of a motor

Answer 13

split ring commutator - turns with the coil. each time the coil reaches a vertical position the commutator swap brushes and flow of current is reversed. this means the direction of force is reversed and the coil keeps spinning in the same direction

Question 14

what can cause a motor to spin faster

Answer 14

1. bring magnets closer
2. use a stronger magnet
3. more turns in a magnet/coil
4. stronger current

Question 15

state the effect of reversing the connections to the battery in a motor

Answer 15

direction of rotation is reversed

Question 16

describe how an EMF is induced in an a.c. generator

Answer 16

1. as the coil rotates one side cuts up the magnetic field lines inducing an e.m.f causing a current to flow
2. when the coil reaches the vertical postion, the side that was cut up is now cut down - induced e.m.f will change direction as well as current

Question 17

what does an alternating current look like on a graph

Answer 17

• similar to sine graph
• V or I on y axis
• time on x axis

Question 18

what is the purpose of a variable resistor

Answer 18

it controls the amount of current passing through a component (e.g. heater) changing its resistance

Question 19

what happens when an ammeter reading decreases

Answer 19

1. batteries go flat

2. resistance increases decreasing current

Question 20

the temperature of a thermistor increases so that its resistance decreases
state the effect of this change on the current - explain your answer

Answer 20

current increases as total resistance of the circuit decreases

Question 21

suggest an advantage of being able to change the current

Answer 21

it prevents overheating

Question 22

describe in terms of current the difference between a big and small wire

Answer 22

big wire: more current and power, less resistance

small wire: less current and power, more resistance

Question 23

what happens when a bigger wire is used instead of a smaller wire

Answer 23

power loss is decreased to about quarter of original power as resistance decreases

Question 24

state 2 sensor devices

Answer 24

LDR

Thermistor

Question 25

describe action in a thermistor

Answer 25

- when temperature increases (not if the thermistor) resistance decreases - when temperature decreases the resistance increases

Question 26

describe action of a LDR

Answer 26

- when light intensity increases resistance decreases | - when light intensity decreases resistance increases

Question 27

what happens to resisitance when V or I or P increases

Answer 27

resistance decreases

Question 28

what is a potential divider

Answer 28

just a circuit with 2 resistors

Question 29

a circuit has a LDR in series with a resistor and a lamp across the resistor what change is made in the circuit to make the lamp glow brightly

Answer 29

-increase current flowing through the lamp by increasing the voltage across it through increasing light intensity of the LDR which will reduce the resistance

Question 30

describe a circuit in series

Answer 30

1. current is the same through out 2. all components are switched on at the same time 3. voltage is shared/divided meaning different brightness in lamps 4. if one lamp is faulty whole circuit breaks

Question 31

describe a circuit in parallel

Answer 31

1. current is divided/shared 2. voltage is the same through out 3. switched on/off individually

Question 32

in a transformer why is the iron core laminated

Answer 32

to reduce energy loss

Question 33

how is an emf induced in a transformer

Answer 33

the a.c. emf at the primary coil induces a magnetic field in the iron core. this alternating magnetic field is cut by the secondary coil producing an EMF in the process

Question 34

formulas in transformers

Answer 34

``` Np/Ns = Vp/Vs VpIp = VsIs ```

Question 35

state 3 methods of charging objects

Answer 35

1. rubbing 2. induction 3. earthing