Cells Emf Internal Resistance

Step 1: Understanding the Concept:
This problem deals with a simple DC circuit containing a real battery (which has both an electromotive force, EMF, and an internal resistance) and an external resistor. The voltage available to the external circuit (the terminal voltage) is the EMF minus the voltage drop across the internal resistance.

Step 2: Key Formula or Approach:
The terminal voltage of a battery supplying a current is given by: where is the EMF of the battery and is its internal resistance.
The voltage across the external resistor is equal to the terminal voltage of the battery.

Step 3: Detailed Explanation:
Given data:
EMF, .
Internal resistance, .
Current in the circuit, .
Calculation:
The voltage across the external resistor is the terminal voltage . We can calculate this using the formula: Substitute the given values:

Step 4: Final Answer:
The voltage across the external resistor will be 10.2 V.