Chapter 3.3 - 'Energy in Electric Circuits'

Question 1

Which part of the battery is the positive side.

Answer 1

Cathode (+)

Question 2

Which part of the battery is the negative side.

Answer 2

Anode (-)

Question 3

What are the three parts in a battery?

Answer 3

Anode (-)
Cathode (+)
Electrolyte

Question 4

Explain how a battery works.

Answer 4

Chemical reactions in a battery cause a build up of electrons at the anode. Resulting in an electrical difference between the anode and cathode.

Question 5

Explain why a circuit needs to be closed.

Answer 5

The electrons want to rearrange themselves to get rid of the difference though the electrolyte keeps them from going straight from the anode to the cathode.

When the circuit is closed, the electrons will be able to get to the cathode.

Question 6

Explain why batteries expire.

Answer 6

The electrochemical processes change the chemicals in anode and cathode to make them stop supplying electrons.

Question 7

Explain what happens when you recharge a battery.

Answer 7

The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and can again provide full power.

Question 8

Define what the difference in charge between two terminals is known as.

ELABORATE.

Answer 8

Potential difference or voltage. This is measured in volts (V)

Question 9

Summarise the energy changes in a light bulb.

Answer 9

1. Chemical energy
   >–TRANSFORMED–>
   electrical potential energy.

2.
Electrical potential energy
>–TRANSFORMED–>
kinetic energy (electrons)

3.
Kinetic energy
>–TRANSFERRED–>
Kinetic energy (filament atoms)

4.
Kinetic energy (filament atoms)
>–TRANSFORMED–>
Thermal energy +light

Question 10

Explain why birds do not get electrocuted on power lines?

Answer 10

Electricity follows the path of least resistance.

Question 11

What is ‘potential difference’ formally defined as?

Answer 11

The amount of electrical potential energy given to each coulomb of charge.

V=E/Q

Where V is the potential difference (V)
E is the electric potential energy (J)
Q is the charge (C)

Question 12

Define ‘electric potential energy’.

Answer 12

E=IxVxt

Where E is the energy provided by the current, same as the work done (J)
V is the potential difference (V)
I is the current (A)
t is the time (s)

Question 13

Define ‘power’.

Answer 13

Measure of how fast energy is converted by the appliance per second.

P=E/t

Where P is the power in joules per second. One joule per second is 1 watt (W).

P=IxV