Ham Radio General Class Practice Test

How many watts are dissipated when a current of 7.0 milliamperes flows through 1.25 kilohms?

1. Approximately 61 milliwatts

2. Approximately 61 watts

3. Approximately 11 milliwatts

4. Approximately 11 watts

The correct answer is: Approximately 61 milliwatts

To determine the power dissipated when a current flows through a resistor, we can use the formula for electrical power, which is given by: \[ P = I^2 \times R \] where \( P \) is the power in watts, \( I \) is the current in amperes, and \( R \) is the resistance in ohms. First, convert the current from milliamperes to amperes: \[ I = 7.0 \, \text{milliamperes} = 7.0 \times 10^{-3} \, \text{amperes} = 0.007 \, \text{amperes} \] Next, convert the resistance from kilohms to ohms: \[ R = 1.25 \, \text{kilohms} = 1.25 \times 10^3 \, \text{ohms} = 1250 \, \text{ohms} \] Now we can plug in the values into the power formula: \[ P = (0.007)^2 \times 1250 \] Calculating \( (0.007)^2 \): \[ (0.007)^2 =