A heating element with a resistance of 12 ohms is connected to 240 V. How much current does it draw?
Answer in A.
Show the answer
20 A
I = E / R = 240 V / 12 ohms = 20 A.
Reference: Ohm's law
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Electrical controls practice questions
35 questions from the hvac fundamentals practice test.
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Electrical controls practice test
10 questions, graded as you go, with the reason for every answer. No sign-up.
What this covers
- Ohm's law
- Power
- Transformers
- Capacitors
- Thermostat terminals
- Contactors
- Compressor windings
- Meter use
- Sequence of operation
- Ladder diagrams
- Control circuits
- Safety switches
- Motors
- Compressor protection
Sample questions
An electric heater draws 20 A at 240 V. Treating it as a purely resistive load, what is its power?
Answer in W.
Show the answer
4800 W
P = E x I = 240 V x 20 A = 4,800 W (4.8 kW).
Reference: Power formula P = E x I
How much current does a 5 kW electric heat strip draw at 240 V? Answer to one decimal place.
Answer in A.
Show the answer
20.8 A
Convert to watts: 5 kW = 5,000 W. I = P / E = 5,000 W / 240 V = 20.8 A.
Reference: Power formula P = E x I