Questions - Power Calculations

Question file 7

  STUDY NOTES       QUESTIONS WITHOUT ANSWERS 

    1. A transmitter power amplifier requires 30 mA at 300 volt. The DC input power is:
      1. 300 watt
      2. 9000 watt
      3. 9 watt
      4. 6 watt
      ========= Answer is c =========
    2. The DC input power of a transmitter operating at 12 volt and drawing 500 milliamp would be:
      1. 6 watt
      2. 12 watt
      3. 20 watt
      4. 500 watt
      ========= Answer is a =========
    3. When two 500 ohm 1 watt resistors are connected in series, the maximum total power that can be dissipated by both resistors is:
      1. 4 watt
      2. 2 watt
      3. 1 watt
      4. 1/2 watt
      ========= Answer is b =========
    4. When two 1000 ohm 5 watt resistors are connected in parallel, they can dissipate a maximum total power of:
      1. 40 watt
      2. 20 watt
      3. 10 watt
      4. 5 watt
      ========= Answer is c =========
    5. The current in a 100 kilohm resistor is 10 mA. The power dissipated is:
      1. 1 watt
      2. 10 watt
      3. 100 watt
      4. 10,000 watt
      ========= Answer is b =========
    6. A current of 500 milliamp passes through a 1000 ohm resistance. The power dissipated is:
      1. 0.25 watt
      2. 2.5 watt
      3. 25 watt
      4. 250 watt
      ========= Answer is d =========
    7. A 20 ohm resistor carries a current of 0.25 ampere. The power dissipated is:
      1. 1.25 watt
      2. 5 watt
      3. 2.50 watt
      4. 10 watt
      ========= Answer is a =========
    8. If 200 volt is applied to a 2000 ohm resistor, the resistor will dissipate:
      1. 20 watt
      2. 30 watt
      3. 10 watt
      4. 40 watt
      ========= Answer is a =========
    9. The power delivered to an antenna is 500 watt. The effective antenna resistance is 20 ohm. The antenna current is:
      1. 25 amp
      2. 2.5 amp
      3. 10 amp
      4. 5 amp
      ========= Answer is d =========
    10. The unit for power is the:
      1. ohm
      2. watt
      3. ampere
      4. volt
      ========= Answer is b =========
    11. The following two quantities should be multiplied together to find power:
      1. resistance and capacitance
      2. voltage and current
      3. voltage and inductance
      4. inductance and capacitance
      ========= Answer is b =========
    12. The following two electrical units multiplied together give the unit "watt":
      1. volt and ampere
      2. volt and farad
      3. farad and henry
      4. ampere and henry
      ========= Answer is a =========
    13. The power dissipation of a resistor carrying a current of 10 mA with 10 volt across it is:
      1. 0.01 watt
      2. 0.1 watt
      3. 1 watt
      4. 10 watt
      ========= Answer is b =========
    14. If two 10 ohm resistors are connected in series with a 10 volt battery, the battery load is:
      1. 5 watt
      2. 10 watt
      3. 20 watt
      4. 100 watt
      ========= Answer is a =========
    15. Each of 9 resistors in a circuit is dissipating 4 watt. If the circuit operates from a 12 volt supply, the total current flowing in the circuit is:
      1. 48 ampere
      2. 36 ampere
      3. 9 ampere
      4. 3 ampere
      ========= Answer is d =========
    16. Three 18 ohm resistors are connected in parallel across a 12 volt supply. The total power dissipation of the resistor load is:
      1. 3 watt
      2. 18 watt
      3. 24 watt
      4. 36 watt
      ========= Answer is c =========
    17. A resistor of 10 kilohm carries a current of 20 mA. The power dissipated in the resistor is:
      1. 2 watt
      2. 4 watt
      3. 20 watt
      4. 40 watt
      ========= Answer is b =========
    18. A resistor in a circuit becomes very hot and starts to burn. This is because the resistor is dissipating too much:
      1. current
      2. voltage
      3. resistance
      4. power
      ========= Answer is d =========
    19. A current of 10 ampere rms at a frequency of 50 Hz flows through a 100 ohm resistor. The power dissipated is:
      1. 500 watt
      2. 707 watt
      3. 10,000 watt
      4. 50,000 watt
      ========= Answer is c =========
    20. The voltage applied to two resistors in series is doubled. The total power dissipated will:
      1. increase by four times
      2. decrease to half
      3. double
      4. not change
      ========= Answer is a =========