Topic 2 - Electricity

Question 1

REMINDER - memorise circuit symbols.

Answer 1

Memorise :)

Question 2

What is the definition for current?

Answer 2

Current is the flow of electrons. It is measured in Amps(A)

Question 3

How are ammeters connected up into a circuit?

Answer 3

Ammeters are connected up in series.

Question 4

What is the defintion for potential difference? (voltage)

Answer 4

THe driving force that pushes the charge around a circuit. Measured in Volts.

Question 5

How are voltmeters connected up into a circuit

Answer 5

They are connected up in parallel

Question 6

What does a voltmeter measure?

Answer 6

A voltmeter measures the difference in the energy of electrons entering a component and the energy of electrons leaving. i.e Potential Difference

Question 7

What is the unit for Charge?

Answer 7

Coulomb (C)

Question 8

What is Charge?

Answer 8

Charge is a property of a body which experiences a force in an electric field.

Question 9

What is the unit of resistance?

Answer 9

Ohms(Ω)

Question 10

What is resistance?

Answer 10

Resistance is opposition to the flow of current. Electrons collide with atoms.

Question 11

What 4 factors affect resistance?

Answer 11

1.Temperature
2.Length
3.Width
4.Material

Question 12

Diodes allow current to flow in both directions true or false?

Answer 12

False - Diodes only allow current to flow in one direction. A diode in the wrong direction has a huge resistance.

Question 13

Go Revise I/V Graphs - Diode

Answer 13

Now.

Question 14

Finish the sentence - Voltage across an ohmic conductor/resistor kept at constant temperature is ….

Answer 14

Voltage across an ohmic conductor/ resistor kept at a constant temperature is directly proportional to the current flowing through it.

Question 15

What is an Ohmic conductor?

Answer 15

Any conductor which follows Ohms law

Question 16

Go revise I/V graphs - resistor!

Answer 16

Now.

Question 17

Go revise I/V graphs - filament lamp!

Answer 17

Now.

Question 18

What is the rule for current in a series circuit?

Answer 18

In a series, current flowing is the same at all places.

Question 19

What is the rule for voltage in a series?

Answer 19

In a series, the voltage across each component adds up to the total voltage of the circuit.

Question 20

What is the rule for current in a parallel circuit?

Answer 20

In a parallel the sum of the currents flowing through the parallel branches equals the current of the whole circuit.

Question 21

What is the rule for voltage in a parallel circuit?

Answer 21

In a parallel, every branch has the same voltage as the power supply/cell.

Question 22

What is the rule for resistance in a series?

Answer 22

In a series, the total resistance is the sum of the resistance of every component.

Question 23

What is the rule for resistance in a parallel?

Answer 23

In a parallel, the more resistors added in parallel the total resistance decreases.

Resistance of a parallel is always LESS than the LOWEST value resistor.

Question 24

What does a thermistor do?

Answer 24

As temperature increases, resistance decreases.

Question 25

What does an LDR do?

Answer 25

As light intensity increases, resistance decreases,

Question 26

What happens when a current is AC?

Answer 26

In AC, the current is constantly changing direction.

Question 27

How are Alternating Currents produced?

Answer 27

ACs are produced by alternating voltages, in which the positve and negative ends keep alternating.

Question 28

What is the frequency of UK mains?

Answer 28

50Hz

Question 29

What are the 3 core cables.

Answer 29

1. Brown - live wire 230V 2. Blue - netral wire 0V 3. Green and Yellow - Earth wire 0V

Question 30

What voltage is UK mains

Answer 30

230V

Question 31

What does the earth wire do?

Answer 31

The earth wire carries current away from the appliance casing, in case that the live wire comes loose.

Question 32

What is the difference between the earth pin vs the live and neutral pins?

Answer 32

The earth pin is slightly longer.

Question 33

What is power??

Answer 33

Power is the rate at which energy is transferred.

Question 34

What is the equation for power loss?

Answer 34

Power loss = current^2 x resistance OR Power loss = voltage x current

Question 35

What are the steps of how power gets from the power station to your home?

Answer 35

1. 25,000V from the power station passes through a step up transformer up to 400,000V. 2. This is to keep current low, so that power loss is low 3. The electricity then reaches a step down transformer, which lowers the voltage to 230V 4. It then goes to peoples homes.

Question 36

What is static electricity caused by?

Answer 36

Static electricity is caused by the friction between 2 insulators, which causes electrons to be transferred from one to the other.

Question 37

What is an electric field?

Answer 37

An electric field is an invisible force around charged objects, it can attract or repel depending on the charge of another object.

Question 38

What does an electric field look like?

Answer 38

The electric field lines go from positive to negative, and get closer together, the nearer the lines are to the negative/positve charge point.