A battery has six cells in series. Each has an emf 1.5 V and internal resistance 1 ohm. If an external load of `24Omega` is connected to it. The potential drop across the load is

Options

A. 7.2 V
B. 0.3V
C. 6.8V
D. 0.4 V

Explanation

To solve the problem step by step, we will follow these calculations:

### Step 1: Determine the total EMF of the battery
Since there are 6 cells in series, each with an EMF of 1.5 V, the total EMF (E) can be calculated as:
\[ E = \text{Number of cells} \times \text{EMF of each cell} = 6 \times 1.5 \, \text{V} = 9 \, \text{V} \]

**Hint:** Remember that when cells are connected in series, their EMFs add up.

### Step 2: Calculate the total internal resistance
Each cell has an internal resistance of 1 ohm. For 6 cells in series, the total internal resistance (r) is:
\[ r = \text{Number of cells} \times \text{Internal resistance of each cell} = 6 \times 1 \, \Omega = 6 \, \Omega \]

**Hint:** Similar to EMF, internal resistances also add up when cells are in series.

### Step 3: Determine the total resistance in the circuit
The external load (R) is given as 24 ohms. The total resistance (R_total) in the circuit is the sum of the internal resistance and the external load:
\[ R_{\text{total}} = R + r = 24 \, \Omega + 6 \, \Omega = 30 \, \Omega \]

**Hint:** Always add internal resistance to the external load to find the total resistance in the circuit.

### Step 4: Calculate the current flowing through the circuit
Using Ohm's law, the current (I) flowing through the circuit can be calculated as:
\[ I = \frac{E}{R_{\text{total}}} = \frac{9 \, \text{V}}{30 \, \Omega} = \frac{3}{10} \, \text{A} = 0.3 \, \text{A} \]

**Hint:** Ohm's law states that current is equal to voltage divided by resistance.

### Step 5: Calculate the potential drop across the load
The potential drop (V_R) across the external load can be calculated using Ohm's law again:
\[ V_R = I \times R = 0.3 \, \text{A} \times 24 \, \Omega = 7.2 \, \text{V} \]

**Hint:** The potential drop across a resistor is the product of the current flowing through it and its resistance.

### Final Answer
The potential drop across the load is **7.2 V**.