Circuits

Question 1

What is a cell

Answer 1

A cell is necessary to push electrons around a complete circuit

Question 2

What is a battery

Answer 2

A battery consists of two or more cells

Question 3

What is a switch

Answer 3

A Switch enables the current in a circuit to be switched on or off

Question 4

What is an indicator

Answer 4

An indicator e.g. a bulb, is designed to emit light as a signal when current passes through it

Question 5

What is a diode

Answer 5

A diode allows current to flow through it in one direction only

Question 6

What is a light emitting diode

Answer 6

A light-emitting diode emits light when a current passes through it

Question 7

What is a fixed resistor

Answer 7

A fixed resistor limits the current in a circuit

Question 8

What is a variable resistor

Answer 8

A variable resistor allows the current to be varied

Question 9

What is a fuse

Answer 9

A fuse is designed to melt and therefore ‘break; the circuit if the current through it is greater than a certain amount

Question 10

What is a voltmeter

Answer 10

A voltmeter is used to measure potential difference

Question 11

What is electricity

Answer 11

Electricity is the flow of charge around a circuit

Question 12

What is the charge carried by

Answer 12

The charge is carried by electrons

Question 13

In which direction does current flow

Answer 13

Current flows from the positive side of the cell to the negative side of the cell

Question 14

In which direction do the electrons flow and why?

Answer 14

Electrons are attracted to the positive side of the cell so therefore flow from the positive side of the cell to the negative side of the cell

Question 15

Define current

Answer 15

Current is the rate of flow of charge (how much charge is flowing per second)

Question 16

A current of 2 amps flows for 10 seconds
Calculate the charge flowing through the circuit and the number of electrons flowing through the circuit

Answer 16

Q = I x t
Q = 2 x 10
Q = 20C

Number of electrons = 20/1.6 x10^-19 = 1.25 x10^20 electrons

Number of electrons = total charge / charge of one electron

Question 17

What is voltage

Answer 17

Voltage provides the force that makes the electrons flow, it also provides energy to the electrons

Question 18

What does an increase in voltage mean

Answer 18

More voltage means more electrons are flowing giving a greater current and more energy goes into the circuit

Question 19

What is voltage in terms of energy and coloumbs

Answer 19

The voltage is the energy carried by one coulomb of charge

Question 20

What is resistance

Answer 20

Resistance in a circuit is caused by the interaction of the electrons and the positive ions

Question 21

Explain why the greater the resistance, the lower the current

Answer 21

When the electrons collide with the positive ions, the flow of electrons decreases, the flow of charge decreases and therefore the current decreases.

Therefore the greater the resistance, the lower the current.

Question 22

Explain how resistance causes an increase in the temperature of the metal

Answer 22

When the electrons collide with the positive ions, they transfer kinetic energy to the positive ions.
The internal energy of the positive ions increases, causing an increase in the temperature of the metal

Question 23

Draw the circuit diagram for investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 23

Include
A variable power supply (a normal power supply with an arrow through it)
An ammeter
A filament lamp
Voltmeter connected to the filament lamp in parallel

Question 24

State the method for investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 24

Increase the voltage from the power supply and record the readings from the ammeter and voltmeter
Repeat each reading twice, and then calculate an average

Question 25

Draw the graph for investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 25

Current on y-axis
Voltage on x-axis
Curve

Question 26

Explain why the current increases when the voltage increases

investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 26

Voltage provides the force that makes electrons flow, it also provides energy to the electrons
Therefore more voltage means more electrons are flowing giving a greater current

Question 27

Explain why the resistance of the bulb increases when the voltage increases

investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 27

As voltage increases, the current increases, there are more collisions between the electrons and positive ions so positive ions gain more energy meaning they vibrate more.
This causes the temperature increases and therefore resistance

Question 28

Explain why the graph curves - for investigating the relationship for current and voltage for a bulb (filament lamp)

Answer 28

Because the resistance increases, the voltage increases at a greater rate than the current, therefore the graph curves.