4.3 Circuits

Question 1

Kirchoff’s Second law

Answer 1

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

Question 2

What law is a consequence of the conservation of energy?

Answer 2

Kirchoff’s second law

Question 3

Formula for resistors in series

Answer 3

R = R1 + R2 + …

Question 4

Formula for resistors in parallel

Answer 4

1/R = 1/R1 + 1/R2 + …

Question 5

What is lost volts equal to?

Answer 5

PD across the internal resistor

Question 6

What formula relates EMF to internal resistance?

Answer 6

ε = IR + Ir

IR is terminal PD
Ir is lost volts

Question 7

Technique to determine internal resistance

Answer 7

Connect the cell with internal resistance in series to an ammeter and variable resistor.
Connect a voltmeter in parallel around the cell.
Vary the resistance, and record values for V and I.
Plot a graph of terminal PD against current.
The y intercept is the EMF, and the negative gradient is the internal resistance.