Electronics

Question 0

How do you find the resistance R of a lamp? State the equation.

Answer 0

R = V/I.

Question 1

Define Resistance.

Answer 1

Resistance = potential difference across a component / current in it.

Question 2

For a filament lamp state the R to I correlation on a graph and explain why the resistance of the lamp varies.

Answer 2

Temperature of the lamp increases with current increase causing an increase in resistance due to more ion vibrations.

Question 3

In a parallel and series set of lamps, if one goes out- what happens to the rest?

Answer 3

Parallel — the lamps get slightly dimmer.

Series — all of the lamps go off.

Question 4

State the equation for E in terms of r, I and R.

Answer 4

E = I(R+r).

Question 5

State and equation for E in terms of V, I and r.

Answer 5

E = V + Ir

Question 6

State Kirchoff’s second law.

Answer 6

The sum of EMF is equal to the sum of PD in a closed loop. Energy is conserved.

Question 7

Suggest why the PD across a fixed resistor in series with a thermistor could increase.

Answer 7

Thermistor has heated up, causing the resistance to drop so that the ratio across the potential divider changes.