Electricity revision

Question 1

what do electric fields cause other charges to experience?

Answer 1

A force

Question 2

what charge does an atom nucleus have?

Answer 2

positive nucleus

Question 3

what surrounds the nucleus?

Answer 3

Electrons

Question 4

TRUE OR FALSE

in a conductor electrons movements are restricted

Answer 4

False

Question 5

Current is measured in what?

Answer 5

Amperes
current symbol (I)

Question 6

Formula for charge?

Answer 6

Current X time

Q=IT

Question 7

What should you remember when dealing with time?

Answer 7

Convert to seconds

Question 8

What device is current measured with?

Answer 8

Ammeter

Question 9

TRUE OR FALSE?

Current is not the same at every point in a series circuit

Answer 9

False

Question 10

How many paths can an electron take in a series circuit

Answer 10

One

Question 11

TRUE OR FALSE?

We can express this rule for current in series circuits using symbols: Is = I1 = I2

Answer 11

True

Question 12

TRUE OR FALSE?

A parallel circuit is one in which there is more than one path for the electrons to take

Answer 12

True

Question 13

what is voltage (potential difference) (V) measured in ?

Answer 13

Volts

Question 14

What is energy measured in?

Answer 14

joule(J)

Question 15

how many volts = 1 joule per coulombs ?

Answer 15

1 Volt

Question 16

What do we use to measure potential difference ?

Answer 16

Voltimeter, connected accross the component

Question 17

TRUE OR FALSE?

The voltage across each component in a series circuit added up is NOT equal to the voltage of the cell/battery

Answer 17

False

We can write this in symbols as Vs = V1 + V2

Question 18

TRUE OR FALSE

Sometimes we need to combine our rules for series and parallel circuits to deal with mixed (complex) circuits

Answer 18

True

Question 19

TRUE OR FALSE ?

To work out total Resistance, we use RT = R1 + R2 + R3

Answer 19

True

Question 20

When adding a resistance to a series circuit, does the resistance increase or decrease?

Answer 20

Increase

Question 21

Does the value of the current in the series circuit increase or decrease when a resistence is added

Answer 21

Decrease

Question 22

what is the formula used in relation to ohms law

Answer 22

V=IR

Question 23

What does each letter stand for in V=IR

Answer 23

V is voltage measured in Volts (V)
I is current measured in Amperes (A)
R is resistance measured in Ohms (Ω)

Question 24

Example 
Calculate the current in this equation 
v= 2V
I=?
R=1kΩ = 1000Ω

Answer 24

I= 0.002A or 2mA (multiply by 1000)

Question 25

What happens when there is a non Ohmic conductor

Answer 25

The resistance of metals increases with temperature. Hence some components (e.g. lamps) will not obey Ohm’s Law as they heat up when more voltage is applied.

Question 26

What does the power rating of an appliance tell us

Answer 26

The power rating of an appliance tells us how much energy it changes every second. e.g. a 2200W kettle changes 2200J of electrical energy into heat every second.

Question 27

Power can be measured using?

Answer 27

Power = Energy P = E | Time t

Question 28

What is power measured in?

Answer 28

Watts (W) and time (t) must be in seconds | a watt is a joule/second

Question 29

What happens when a current and voltage are known through an appliance

Answer 29

When the current through an appliance and the voltage across it are known, the power can be calculated using: Power = Current x Voltage P = I x V (PIV)

Question 30

What is the fuse main purpose

Answer 30

The fuse protects the flex from overheating. It melts and breaks the circuit if the current gets too high.

Question 31

What is the general rule for fitting fuses to plugs for appliances

Answer 31

Power rating > 720W, use 13A fuse. Power rating < 720W, use 3A fuse.

Question 32

TRUE OR FALSE? | In a direct current, the electrons can flow in different directions

Answer 32

False

Question 33

TRUE OR FALSE | in alternating current, the flow of electrons is constantly changing directions to and from

Answer 33

True

Question 34

How do we measure Hertz ?

Answer 34

The number of times that the current changes direction every second is called the frequency of the AC supply and this is measured in hertz (Hz).

Question 35

What frequency is mains electricity ? | IMPORTANT

Answer 35

50Hz

Question 36

How can we identify electrical signals to confirm whether they are AC or DC

Answer 36

oscilloscope

Question 37

what does LED stand for

Answer 37

light emitting diode

Question 38

is LED an input or output device

Answer 38

An LED is an output device, changing electrical energy into light.

Question 39

How many ways can a current pass through an LED

Answer 39

One way

Question 40

Why is a resistor connected in series in an LED

Answer 40

Too much current will damage the LED so a resistor is added to reducde the current