Topic 2 - Electricity

Question 1

What is Alternating Potential Difference?

Answer 1

A continually oscillating current flow, which
results in the potential difference across two points continually oscillating between a positive and negative value.

Question 2

What are are Amps?

Answer 2

The unit that is used for current.

Question 3

What is attraction?

Answer 3

A force pulling two opposite charges together, when they are brought near each other.

Question 4

What is a coulomb?

Answer 4

The units that are used for charge.

Question 5

What is a diode?

Answer 5

A component that only allows current to flow through in the forward
direction. They have very large resistances in the reverse direction.

Question 6

What is Direct Potential Difference?

Answer 6

A one directional current flow.

Question 7

What is the earth wire?

Answer 7

The green and yellow striped safety wire that prevents an appliance from becoming live.

Question 8

What are electric field lines?

Answer 8

Line representing an electrical field, that point in the direction in which a positive charge would experience an electric force.

Question 9

What is an electric field?

Answer 9

A region in which a charge will experience a non-contact, electric force. All charged objects have an electric field around them, and this field is stronger the closer you are to the charge.

Question 10

What is an electrical current?

Answer 10

The rate of flow of electrical charge. It’s value is the same at any position in a single closed loop.

Question 11

What is electrical work?

Answer 11

When charge flows in a circuit, electrical work is said to be done.

Question 12

What is a filament lamp?

Answer 12

A light emitting component consisting of an enclosed metal filament. Its resistance increases as the filament’s temperature increases.

Question 13

What is insulation?

Answer 13

The coating around power cables that prevents electrocution and is
colour coded to allow for easy identification.

Question 14

What is an Light Dependent Resistor (LDR)?

Answer 14

A light sensitive component whose resistance increases as its temperature decreases.

Question 15

What is a live wire?

Answer 15

The brown coloured wire that carries the alternating current from the supply in a mains power supply.

Question 16

What is mains electricity?

Answer 16

An ac supply, which in the UK has a frequency of 50Hz a value of 230V

Question 17

What is a neutral wire?

Answer 17

The blue coloured wire that completes the circuit in a mains power supply.

Question 18

What is a Non contact force?

Answer 18

A force experienced between two separated objects. Examples include gravity, and magnetic and electric forces.

Question 19

What is a Ohmic Conductor?

Answer 19

A conductor whose current flow is directly proportional to the potential difference across it, when held at a constant temperature.

Question 20

What is Ohms?

Answer 20

It is the unit that is used for resistance.

Question 21

What does parallel mean?

Answer 21

Components connected in parallel have the same potential difference across each component. The total current is equal to the sum of the currents flowing through each component.

Question 22

What does potential difference mean?

Answer 22

The product of a component’s resistance and the magnitude of current flow through it.

Question 23

What does repulsion mean?

Answer 23

Caused when two like-charges are brought near each other.

Question 24

What is resistance?

Answer 24

A measure of the opposition to current flow.

Question 25

What does the phrase 'resistors in parallel' mean?

Answer 25

The total resistance is equal to the inverse of the sum of the inverses of the resistance of the parallel components. The total resistance of two parallel resistors is always less than the lowest individual resistor value.

Question 26

What does the phrase 'resistors in series' mean?

Answer 26

The total resistance is equal to the sum of the resistances of the individual components.

Question 27

What does series mean?

Answer 27

Components connected in series have the same current passing through each component but share the total potential difference of the power supply.

Question 28

What does static charge mean?

Answer 28

The charge caused by an imbalance of positive and negative charges in, or on, an object’s surface. It is often caused by electrons being rubbed from one surface onto another.

Question 29

What is a step down transformer?

Answer 29

Devices found between the transmission cables and the consumer that lower the potential difference of the power so it is at safe, usable levels.

Question 30

What is a step up transformer?

Answer 30

Devices that increase the potential difference generated by a power station, so that the electrical power transmitted along the transmission cables is at a higher potential.

Question 31

What is the national grid?

Answer 31

The network of power stations, transformers and cables that connect consumers to power stations.

Question 32

What is a thermistor?

Answer 32

A temperature dependent component, whose resistance increases as its temperature decreases.

Question 33

What is a volt?

Answer 33

It is the unit that is used for potential difference.

Question 34

What two factors does the current in a circuit depend on?

Answer 34

- Potential Difference (V) - Resistance (R)

Question 35

What is an ohmic conductor and state the conditions that are required?

Answer 35

- A conductor for which current and potential difference are directly proportional - Resistance remains constant as current changes - Temperature must be constant

Question 36

List four components for which resistance is not constant as current changes?

Answer 36

- Lamps - Diodes - Thermistors - Light Dependant Resistors

Question 37

How does the potential difference across two components vary when connected in series and parallel?

Answer 37

- Series: Total P.D is shared between each component - Parallel: P.D across each component is the same.

Question 38

If two resistors are connected in parallel, what can be said about their combined total resistance?

Answer 38

Their total resistance is less than the smallest of the two individual resistance.

Question 39

If two resistors are connected in series, what can be said about their total resistance?

Answer 39

Their total combined resistance is equal to the sum of the two individual resistances.

Question 40

How should you connect an ammeter in a circuit to measure current?

Answer 40

Ammeters should be connected in series with the component that they are measuring current through.

Question 41

How should you connect a voltmeter in a circuit to measure potential difference?

Answer 41

Voltmeters should be connected in parallel to the component that they are measuring the potential difference of.

Question 42

Define alternating current and direct current?

Answer 42

- Alternating current: Current that continuously changes direction at a specific frequency - Direct current: One directional current flow

Question 43

What two main factors does amount of energy transferred by an appliance depend on?

Answer 43

- How long the appliance is being used for - The power of the appliance

Question 44

Why do transmission lines transfer electricity at high potentials?

Answer 44

- A high potential, results in a low current - The lower the current, the less energy that is wasted as heat - Therefore it is more efficient

Question 45

Why does the potential need to be decreased between transmission lines and houses?

Answer 45

- Lower potentials are safer for domestic use and reduces the likelihood of severe electrocution - Appliances are designed for 230V

Question 46

Why can insulators become electrically charged when rubbed together?

Answer 46

- Electrons are rubbed from one material onto the other - The material gaining electrons becomes negatively charged - The material losing electrons becomes equally positively charged

Question 47

In situations where sparks are unwanted, what precaution must be taken to prevent the build up of static charge?

Answer 47

Any surfaces that are rubbing against each other should be earthed to allow the charge to flow off the material.