Electricity and Circuits

Question 1

Definition of current

Answer 1

Current is the flow of electric charge around a circuit

Question 2

What allows current to flow?

Answer 2

It will only flow through an electrical component with a potential difference across that component and is the circuit is complete

Question 3

Definition of potential difference (voltage)

Answer 3

The driving force that pushes the charge round

Question 4

Definition of resistance

Answer 4

Anything that slows the flow down

Question 5

In metals how are currents formed?

Answer 5

The flow of electrons

Question 6

How is the measurement of current?

Answer 6

Amperes

Question 7

What is the measurement of charge?

Answer 7

Coulombs

Question 8

What is the measurement of time?

Answer 8

seconds

Question 9

What usually increases when temperature increases?

Answer 9

Resistance

Question 10

How does the resistance increase the temperature?

Answer 10

• current flows through the resistor
• the electrons collide with the ions in the lattice structure
• the ions vibrate and heat up
• the more they vibrate the harder it is for the electrons to get through the resistors as there are more collisions
• if the resistor gets too hot no current will flow through

Question 11

What does the ammeter measure?

Answer 11

The current flowing through a component

Question 12

What does the voltmeter measure?

Answer 12

The voltage in across the component

Question 13

What is an LDR?

Answer 13

• Light Dependent Resistor
• As the light increases the resistance decreases
• As the darkness increases the resistance increases
• e.g. Automatic night lights and burglar detectors

Question 14

What is a Thermistor?

Answer 14

• A temperature dependent resistor
• in hot conditions the resistance drops
• in cool conditions resistance rises
• useful for temperature detectors

Question 15

What happens to resistance of a circuit when you add resistors?

Answer 15

• the total resistance increases
• the circuit has to share the total p.d. between the resistors
• the current is reduced

Question 16

What are the Uk main supply of electricity in homes?

Answer 16

• 230v
• a.c
• the frequency is 50Hz

Question 17

What is the function of the neutral wire?

Answer 17

• blue
• completes circuit
• current flows through live and neutral wire
• It is around 0V

Question 18

What is the function of the live wire?

Answer 18

• brown
• carries voltage
• it alternates between + and - voltage
• Around 230v

Question 19

What is the function of the an earth wire?

Answer 19

• green and yellow
• the wire is for safety and protecting wiring
• it carries the current away if something wrong happens in the circuit