Electricity

Question 1

The power of a device is

Answer 1

The rate at which it transforms energy

Question 2

Electrical heating examples

Answer 2

Toaster, cooker, washing machine, tumble dryer, heater and hair dryer

Question 3

Electrical heating process

Answer 3

As a stream of electrons passed through a conductor, the electrons collide with the atoms that make up the conductor and lose kinetic energy which caused an increase in the temperature of the conductor

Question 4

The longer the length of a wire

Answer 4

The higher the resistance

They are directly proportional

Question 5

Direct current

Answer 5

Current that always passing in the same direction

Cells and batteries supply it

Question 6

Alternating current

Answer 6

A current that is constantly changing direction and alternates between a positive and a negative voltage.

Question 7

UK mains supply is

Answer 7

230 V

Voltage is alternating

Question 8

Dangers of electricity

Answer 8

• damaged plug, damaged insulation or frayed cables
• overheating cables
• damp conditions
• loosely connected wires
• long cables
• pushing metal objects into sockets

Question 9

Fuses

Answer 9

A short piece of thin wire

If the current is too large, the wire gets hot and melts the fuse. This breaks the circuit and effectively switches off the current.

Question 10

Circuit breakers

Answer 10

A circuit breaker can detect when current through two wires is different ( an earth leakage) can break the circuit

Question 11

Circuit breakers V fuses

Answer 11

Circuit breakers have a number of advantages over uses.

They are easily reset (no melted fuse wire to replace)

Circuit breakers can break an overloaded circuit much faster than a fuse

Question 12

The earth wire

Answer 12

Connected to the outer metal case of an appliance

If the live wire of an appliance becomes detached and touches the outer metal case, the earth wire prevents it from being hazardous to the user.

Question 13

Series circuit

Answer 13

• current same
• voltage shared, add voltage to get total.
• add resistant to get total resistance

Question 14

Parallel circuit

Answer 14

• current shared, add current to get total.
• voltage the same
• add 1/resistance then turn the fraction around to get total resistance.

Question 15

Double insulation

Answer 15

Articles with outer cases

Question 16

Fixed resistor

Answer 16

Resistance is fixed

Question 17

Variable resistor

Answer 17

Resistance can be varied

Question 18

Thermistor

Answer 18

Resistance varies with temp

Question 19

Thermistor with changing temp

Answer 19

When the temp is high the resistance is low and vice versa

Question 20

Light dependent resistor

Answer 20

The resistance varies with light intensity

Question 21

LDR with light intensity

Answer 21

When the light is high the resistance is low and vice versa

Question 22

Diode

Answer 22

Only allows current to flow in one direction. From positive to negative

Question 23

Light emitting diode

Answer 23

Only allows current to flow in one direction. (From positive to negative) Light is emitted when current flows through it.

Question 24

insultation

Answer 24

electrical insulators do not contain free charge carries and as a result electric current can’t pass through them

Question 25

Ohm’s law states that

Answer 25

the electrical current (I) flowing in an circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, if the voltage is increased, the current will increase provided the resistance of the circuit does not change.

Question 26

ohms law summed down

Answer 26

if we increase the voltage, then the current will increase. But, if we increase the resistance, then the current will decrease.

Question 27

voltage is the energy transferred per unit

Answer 27

charge passed

Question 28

a volt is a joule per

Answer 28

coloumb

Question 29

why should you always use a fuse one higher

Answer 29

otherwise it will blow

Question 30

electirc current is the rate of flow of

Answer 30

charge

Question 31

backwards s symbol represents

Answer 31

alternating current

Question 32

current is the

Answer 32

rate of flow of charge

Question 33

what flow through a circuit

Answer 33

electrons

Question 34

why do they flow from negative to positive

Answer 34

because they are negatively charged an attracted to the positive

Question 35

why is water dangerous near electrics

Answer 35

because it is a good conductor

Question 36

parallel circuits, the voltage across each component is

Answer 36

the same as the voltage of the battery.

Question 37

in parallel circuits the current

Answer 37

the current is shares and divided between the electrical components it supports. I.e. if there are two bulbs u would half it, but if there are 3 bulbs on one and 1 bulb on the other, you would divide it by 3

Question 38

to find the resistance in parallel circuits

Answer 38

add together 1/r1, 1/r2, 1/r3 etc and then flip the fraction for your answer!

Question 39

in series the current

Answer 39

is the same

Question 40

This means the resistance in a wire increases as:

Answer 40

the length of the wire increases

the thickness of the wire decreases

Question 41

in series the resistance

Answer 41

is shared, just the total sum

Question 42

in series the voltage

Answer 42

is the sum of the voltages across each component

Question 43

conventional flow flows from

Answer 43

the opposite direction of electron flow