A motor of power 60 W draws current 5 A from a source of 15 V. What is loss of power ?

Options

A. (a)30 W
B. (b)25 W
C. (c)20 W
D. (d)15 W

Answer

To solve the problem of finding the loss of power in the motor, we will follow these steps:

### Step 1: Identify the given values
- Power of the motor (P_motor) = 60 W
- Current drawn (I) = 5 A
- Voltage source (V_source) = 15 V

### Step 2: Calculate the resistance of the motor
Using Ohm's Law, we know that:
\[ V = I \cdot R \]
Rearranging this gives us:
\[ R = \frac{V}{I} \]
Substituting the values we have:
\[ R = \frac{15 \, \text{V}}{5 \, \text{A}} = 3 \, \Omega \]

### Step 3: Calculate the power consumed by the motor using the resistance
The power consumed by the motor can also be calculated using the formula:
\[ P = I^2 \cdot R \]
Substituting the values we have:
\[ P = (5 \, \text{A})^2 \cdot 3 \, \Omega \]
\[ P = 25 \cdot 3 = 75 \, \text{W} \]

### Step 4: Calculate the loss of power
The loss of power can be calculated by subtracting the power of the motor from the power consumed:
\[ \text{Power Loss} = P_{\text{consumed}} - P_{\text{motor}} \]
Substituting the values:
\[ \text{Power Loss} = 75 \, \text{W} - 60 \, \text{W} = 15 \, \text{W} \]

### Conclusion
The loss of power in the motor is **15 W**.

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