Resistance

Question 1

Why does the current in a circuit change over time?

Answer 1

The current in a circuit changes over time because the temperature of the wire increases as a result of heating caused by the current. As temperature increases, resistance increases.

Question 2

What is resistance?

Answer 2

Resistance is the measure of how much the material or components resists the flow of current in a circuit. Resistance opposes the flow of current, they are inversely proportional.

Question 3

What is an ohm defined as?

Answer 3

The resistance of a component when a p.d of 1V is produced per ampere of current

Question 4

Why does resistance increase when temperature increases?

Answer 4

• As temperature rises, the atoms in a conductor vibrate more vigorously because they gain thermal energy.
• These vibrations increase the likelihood of collisions between free electrons (the charge carriers) and the vibrating atoms.
• Each collision impedes the flow of electrons, effectively increasing resistance.

Question 5

What is ohm’s law?

Answer 5

V = IR, for a metallic conductor kept at constant temperature, the current in the wire is directly proportional to the pd across its ends.

Question 6

What are the I-V characteristics of a resistor?

Answer 6

The current is directly proportional to potential difference. The resistance of the resistor is constant.

Question 7

What are the I-V characteristics of a filament lamp

Answer 7

The resistance is not constant. This is because as the current increases, there’s in increase in the amount of collisions, increasing resistance.