Section 5 - Electricity And Circuits (Unfinished)

Question 1

Define the term current

Answer 1

It is the rate of flow of electric charge (electrons) through a circuit

Question 2

What is the unit for current?

Answer 2

Ampere, A

Question 3

What is the potential difference?

Answer 3

Is the energy per unit of charge that is transferred by the component

Question 4

What is potential difference measured in?

Answer 4

Volts, V

Question 5

What is resistance?

Answer 5

The ratio of voltage over current - it is how much the current is limited

Question 6

What is the unit for resistance?

Answer 6

Ohms, Ω

Question 7

How does potential difference generally affect the current?

Answer 7

The higher the potential difference, the higher the current

Question 8

How does resistance affect the current?

Answer 8

The greater the resistance, the lower the current

Question 9

What is the equation for charge?

Answer 9

Charge = current x time

Question 10

How do you calculate energy transferred?

Answer 10

Energy transferred = charge moved x potential difference

Question 11

How much does one volt equal in a joule our coulomb?

Answer 11

One volt = 1 joule per coulomb

Question 12

How do you calculate potential difference?

Answer 12

Potential difference = current x resistance

Question 13

What factor usually affects resistance?

Answer 13

Temperature

Question 14

Why does the temperature increase when an electrical charge flows through a component?

Answer 14

Because work needs to be done against resistance, causing friction in the wires

Question 15

What does dissipated mean?

Answer 15

Energy is lost to the surroundings

Question 16

Why does the temperature of a resistor increase when a current flows through it?

Answer 16

The electrons collide with the ions in the lattice that make up the resistor, and this gives the ions more energy which causes them to vibrate and heat up

The more the ions vibrate, the harder it is for the electrons to get through the resistor, because there are more collisions

This means that the for a given potential difference, the current decreases when a resistor heats up

Question 17

What affect does temperature have on a thermistor?

Answer 17

The resistance of the thermistor decreases as the temperature increases

Question 18

What is an LDR?

Answer 18

A light dependent resistor

In bright light, the resistance falls

In dim light, the resistance increases

Question 19

What are some common uses of LDR’s?

Answer 19

• Automatic night lights
• Outdoor lighting
• Burgular detectors

Question 20

What is a thermistor?

Answer 20

A temperature dependent resistor

In hot conditions, the resistance drops

In cold conditions, the resistance increases

Question 21

What are some common uses of thermistors?

Answer 21

Electronic thermometers

Question 22

What is a series circuit?

Answer 22

In a series circuit, the different components are connected in a line, end to end

If you remove one component, then the whole circuit no longer functions and is broken

Question 23

What is the current in a series circuit?

Answer 23

The current in a series circuit is the same, no matter what point you place an ammeter in the circuit

Question 24

What happens to the total resistance in a series circuit when you add resistors?

Answer 24

The total resistance increases

Question 25

What is a parallel circuit?

Answer 25

In a parallel circuit, each component is separately connected to the supply

If you remove one component, it will hardly affect the others, and the circuit will still work

Question 26

Which is more commonly used - series or parallel circuits?

Answer 26

Parallel circuits - for example in household electrics - you don’t have one switch for the entire house. you have different switches which turn off different lights in different areas of the house, which is why parallel circuits are used as they are more convenient and can be used in a wider range of applications

Question 27

Is the current the same across the whole circuit in a parallel circuit?

Answer 27

No - the energy in the circuit stays the same, but the energy is split at the different junctions. The energy going into these junctions will be added up to show that the energy in the circuit still never changes - it just gets split up for the different components

Question 28

What happens to the total resistance in a parallel circuit if you add resistors?

Answer 28

The total resistance decreases