electricity

Question 1

what is charge? what are the units

Answer 1

measured in Coulombs (C). One electron has a charge of 1.6x10-19 C. 1 Coulomb is defined as the amount of charge that passes in 1 second when the current is 1 Ampere.

Question 2

what is current?

Answer 2

the rate of flow of charge, and is measured in Amperes (A). A current of 1A means that 1 coulomb of charge flows past that point every second (hence the term “rate”). Current can only flow if there is a potential difference. It is measured with ammeters which are placed in series within a circuit

Question 3

what is potential difference?

Answer 3

measured in volts (V), and is the work done per unit charge. It is measured by voltmeters that are placed in parallel and have infinite resistance, so they measure current between 2 points in a circuit.

Question 4

what is resistance?

Answer 4

measured in Ohms (Ω). It slows down the current passing through the circuit.

Question 5

what is power?

Answer 5

measured in watts (W) and is defined as the rate of transfer of energy

Question 6

how are cell connected in series and parallel different?

Answer 6

series- total voltage is the sum of individual voltages
parallel- total voltage is equal to one cell

Question 7

what’s the point in having cells connected in parallel if the voltages don’t sum?

Answer 7

There are two main reasons - firstly, the batteries each last twice as long as they would if they were connected in series, and secondly, if one of the batteries were to die/break, the circuit would still be operational.

Question 8

what is the equation that links potential difference (V), current (I) and resistance (R)?

Answer 8

V=IR

Question 9

how do resistors differ in series and parallel?

Answer 9

series- their resistances are added together to get the total resistance.
parallel- total resistance is less than individual resistor

Question 10

why are cells different in series and parallel?

Answer 10

-In series, each ‘push’ (voltage) that the batteries provide is different so they are added together.
-In parallel, an electron can only ever go through one cell in each ‘lap’ of the circuit, so it only gets one push

Question 11

How does current differ in series and parallel circuits?

Answer 11

series- current is the same throughout the circuit
parallel- the sum of currents flowing into a junction must equal the sum of currents leaving the junction (Kirchoff’s First Law)

Question 12

how does voltage differ in a series and parallel circuit?

Answer 12

series- total voltage supplied by the cell is divided between the components
parallel- the voltage supplied by the cell is the same as the voltage across each component in the circuit.

Question 13

what does it mean by short circuit?

Answer 13

the charge bypasses the component by taking the path of least resistance

Question 14

what is a diode?

Answer 14

a device allowing the flow of current in one direction

Question 15

what happens if the arrow of the diode is pointing in opposite direction to the current?

Answer 15

the diode is in “reverse bias” and no charge can pass through

Question 16

how does current flow?

Answer 16

from positive to negative

Question 17

what is a transformer?

Answer 17

a device that changes voltage and current, whilst keeping power the same

Question 18

what is the equation where n1 is the number of turns on the primary coil and n2 is the number of turns on the secondary coil. Naturally, v1 and v2 are each coil’s respective voltage.

Answer 18

n1/n2=V1/V2

Question 19

what happens If the secondary coil has more turns than the primary?

Answer 19

the voltage is stepped up (ie: increased) and the current is decreased

Question 20

what happens if the primary coil has more turns?

Answer 20

then the voltage is decreased (this is helpful when electricity has reached houses to step it down to a more manageable voltage) and the current is increased.

Question 21

transformers only work with what kind of current?

Answer 21

Alternating Current (AC). They do NOT work with Direct Current (DC).

Question 22

voltage is only created when?

Answer 22

he magnet is moving. Moving the magnet in one direction would generate a positive voltage, whereas moving it in the other direction would generate a negative voltage.

Question 23

what happens when you keep moving the magnet backwards and forwards through the coil?

Answer 23

you create a potential difference that keeps on changing direction - an Alternating Current (AC).

Question 24

how do generators work?

Answer 24

by spinning the magnet in the coil instead of moving it in and out

Question 25

what are the 4 factors influencing the size of induced voltage?

Answer 25

1)The speed of rotation of the magnet (or coil)
2)The size of the magnetic field
3)Having more turns of wire on the coil
4)The area of the coil

Question 26

how do the 4 factor influence the size of induced voltage?

Answer 26

If you spin the magnet (or coil) faster, you get more voltage produced. If you have a stronger magnet, you get more voltage produced. And if you have a bigger coil (more turns and/or greater area), you get more voltage produced.

Question 27

how do you get a higher current from an AC generator?

Answer 27

-Increase the speed of rotation
-Increase the strength of the magnet
-Increase the number of turns of the coil
-Increase the area of the coil
-Keep the coil perpendicular to the magnetic field
-keeping the coil perpendicular to the magnetic field

Question 28

how do you work out the direction of current in a generator?

Answer 28

using Flemings right hand rule.
-The ThuMb shows the direction of Motion.
-The First Finger shows the direction of the Field.
-The SeCond finger shows the direction of the Current.

Question 29

can insulators let electrons flow through them?

Answer 29

no and so clumps of electrons build up on the surface of insulators.

Question 30

what happens when you rub two insulators?

Answer 30

electrons can get transferred between them. So one of the items loses electrons (and becomes positively charged), and the other one gains electrons (and becomes negatively charged).

Question 31

what does it mean by earthing objects?

Answer 31

connecting them to the ground using an electrical conductor. That way, static electricity won’t be an issue because charge would never build up on the item. Instead, it would flow through the conductor and be absorbed by the ground.

Question 32

what are the uses of static electricity?

Answer 32

-Pollution control: collecting pollutants
-printing
-spray painting