q4 calculate the following

Question

A battery of 10 primary cells has an open-circuit emf 0f 15V. When a 30 ohm resistor is connected across the battery, the terminal pd is 12V. Calculate: 1. The current 2. The internal resistance per cell 3. The power in the external circuit

Answer 1

1)

Step 1:

The emf of the 10 primary cell is 15 V.

The Load resistance connected across the cell is .

The terminal potential difference is 12 V.

The voltage across the load is defined as .

Voltage across the load is equal to the potential difference across the terminal of the battery.

The supplied current .

Solution:

The supplied current .

Answer 2

2)

Step 1:

Suppose that the battery with emf  and internal resistance supplies a current  through an external load resistor , then the potential difference across the battery is .

Substitute , and in .

The overall internal resistance is .

Internal resistance per cell is .

Solution:

Internal resistance per cell is .

Answer 3

3)

Step 1:

Power in the external circuit :

Power can be calculated using the relation : .

Where is emf of the battery,

          is current through the circuit,

Therefore, the power in the external circuit is 6 W.

Solution:

The power in the external circuit is 6 W.