P13: Direct Current Circuits

Question 1

How to calculate the total EMF of cells?

Answer 1

In series:
-E(total) = E1 + E2 + E3 +…
In parallel:
-E(total) = E1 = E2 = E3 = …

Question 2

What other equations can be derived from E = I(R + r)?

Answer 2

• E = V + v
• V = E - v
• V = E - Ir

Question 3

What is EMF?

Answer 3

The amount of electrical energy produced by the battery for each coulomb of charge. (V)

Question 4

What is meant by terminal p.d.?

Answer 4

The potential difference across the load resistance R is the energy transferred when one coulomb of charge flows through it.

If there is no internal resistance, this will be equal to the EMF of the cell.

Question 5

Kirchoff’s 2nd law:

(about emf)

Answer 5

The total emf around a series circuit =
The sum of the p.d.s across each component

Question 6

The total current entering a junction = ?

(Kirchoff’s 2nd law)

Answer 6

= the total current leaving that junction

Question 7

Total R in a series circuit can be found with…?

Answer 7

R(total) = R1 + R2 + R3 +…

Question 8

What does potential divider mean?

Answer 8

A circuit with a voltage source and some resistors in series.

A variable resistor can be used if you need a varying p.d. supply.