Circuits

Question 1

How do electric circuits work?

Answer 1

Conductors contain free charges (electrons), which are free to move. These electrons allow the electric charge to flow. Current can’t flow in insulators as there are no free electrons that can move. The loop is continuous.

Question 2

Are charges used up in circuits ?

Answer 2

No.

Question 3

Charges pass from the … To … Side of the cell

Answer 3

Positive, negative.

Question 4

Current relies on… To flow.

Answer 4

Voltage.

Question 5

What is voltage?

Answer 5

The driving force.

Question 6

What is resistance ?

Answer 6

This opposes the flow of electrons, can be opponents that resist.

Question 7

More voltage means…

Answer 7

More current !

Question 8

More resistance =

Answer 8

Less current!

Question 9

What is power ?

Answer 9

The rate at which energy is transferred to an appliance.

Power (watts) = voltage (v) x current (a)

Question 10

What are the rules in a series circuit? Why?

Answer 10

Voltage adds up as it is shared between different components. The work done on the charge equals work done by the charge.
Current is the same everywhere as the same current flows around all parts of the circuit.
Resistance adds up as the resistance of two resistors is greater than that of one alone - the battery has to push charge through all of them. The bigger the resistance - the greater its share of PD.

Question 11

If the resistance of one component changes….

Answer 11

The potential difference across all components will change too.

Question 12

Why do cell voltages add up when cells are added in series?

Answer 12

Each charge in the circuit passes through all the cells and gets a push from each cell.
Each charge in parallel only goes through one cell so if two cells are added the voltage stays the same.

Question 13

Adding cells increases … Without increasing … Which means that the total … Increases.

Answer 13

Voltage, resistance, current.

Current stays the same across the circuit.

Question 14

Adding cells in parallel also increases total … But the current through each cell is ..: than in the rest of the …. As they join together to make the total …

Answer 14

Current, less, circuit, current.

Question 15

What is current?

Answer 15

A flow of charge.

Question 16

In parallel circuits if one of the components is removed or disconnected it doesn’t affect other components at all as …

Answer 16

They are separately connected to the cell.

Question 17

Give examples of devices connected by parallel circuits…

Answer 17

Cars and household electrics. You have to be able to turn things on and off separately.

Question 18

PD is equal across all components because…

Answer 18

The total resistance does not add up, meaning that the total potential difference is the same across the components. This means that identical bulbs connected in parallel are the same brightness.

Question 19

Current is shared. Why?

Answer 19

The current is the same flowing from the battery to the current flowing to the battery. The current is shared between the branches so the current splits.
A = A1+A2

Question 20

Resistance is tricky. The total resistance is always less than the branch with the smallest resistance. Why?

Answer 20

This is because the charge has more than one branch to take - only some charge will flow along each branch so a circuit with two resistors in parallel will have a lower resistance than a series circuit with the resistor on its own. This means a higher power.

Question 21

Each component in a parallel circuit is separately connected to the battery which means…

Answer 21

The current through each component is the same as if that component was the only one in the circuit.

Question 22

Why do thinner filament wires light up but thicker wires do not?

Answer 22

Thinner wires have less space for the charge to go. The electrons are more likely to collide with the positive ions, causing them to vibrate. As a result, more energy is transferred to the positive ions, resulting in a higher temperature and so more light produced.