Ohm's Law Practice Test 1

Question 1: what is the current drawn by electric heater rated 1800 watts at 120 volts?

• 15 Amperes
• 10 Amperes
• 18 Amperes
• 8 Amperes

Question 2: A 120 volt circuit which has a resistance of 12 ohms draws a current of 10 A. If the voltage is doubled, the current in the circuit ..............

• increases
• decreases
• remains same

Question 3: A 6 AWG THHN conductor is good for use for how many KW of load at 120 volts?

• 7.8
• 7800
• 780
• 78

NEC Reference: NEC 310.15(B)(16)

Question 4: A light bulb has a rating of 100 W at 115 volts. What is the current drawn by it when it is connected to source voltage of 115 volts?

• 0.87 amperes
• 0.97 amperes
• 0.92 amperes
• 0.8 amperes

Question 5: How much power is consumed by 240 volts circuit that draws 20 A current?

• 4.8 KW
• 4800 KW
• 3500 W
• 3800 KW

Question 6: What is the resistance of an electric heater rated 1800 watts at 120 volts?

• 8 ohms
• 10 ohms
• 12 ohms
• 15 ohms

Question 7: An ohm meter indicates a resistance of 120 volt electric heater to be 8 ohms. what is the current drawn by the heater?

• 15 Amperes
• 10 Amperes
• 8 Amperes
• 18 Amperes

Question 8: If a single phase circuit feeding residential electric heaters, what is the maximum allowable wattage that can be connected?

• 2880 Watts
• 3600 Watts
• 2400 Watts
• 1800 Watts

Question 9: A 3000 watts electric oven is connected to 480 volt circuit what is the resistance of heating element?

• 76.8 ohms
• 6.25 ohms
• 58.3 ohms
• 12.8 ohms

Question 10: An electric motor rated at 3600 watt is connected to 240 V single phase , 2 wire circuit what is the current flow in the circuit?

• 15 amperes
• 10 amperes
• 7.5 amperes
• 12 amperes

Question 11: An electric heater with a resistance of 16 ohms, which draws a current of 7 amps. What is the minimum wattage of electric heater?

• 784 watts
• 112 watts
• 786 watts
• 156 watts

Question 12: Three resistors of 10 Ω, 20 Ω, and 30 Ω are connected in SERIES. What is the total resistance?

• 20 ohms
• 60 ohms
• 600 ohms
• 6 ohms

Question 13: Two 10 Ω resistors are connected in PARALLEL. What is the total resistance?

• 20 ohms
• 10 ohms
• 5 ohms
• 2 ohms

Question 14: A 120 V supply is connected across two resistors in series: 40 Ω and 80 Ω. What is the voltage drop across the 80 Ω resistor?

• 40 V
• 60 V
• 80 V
• 120 V

Question 15: In a PARALLEL circuit, the voltage across each branch is:

• The same as the supply voltage across every branch
• Different in every branch, but the current is equal
• Always zero
• Only present in the branch with the highest resistance

Question 16: In a SERIES circuit, the current flowing through each component is:

• The same everywhere in the circuit
• Different at each component
• Always zero
• Only flows through the largest resistor

Question 17: If the length of a copper wire is doubled, while its material and cross-sectional area stay the same, its resistance:

• Doubles
• Is cut in half
• Stays exactly the same
• Becomes four times as large

Question 18: If the cross-sectional area of a copper wire is doubled, while its length and material stay the same, its resistance:

• Doubles
• Is cut in half
• Stays exactly the same
• Becomes zero

Question 19: As the temperature of a copper conductor increases, its electrical resistance:

• Increases
• Decreases
• Stays exactly the same
• Becomes negative

Question 20: Ohm's Law (V = IR with a constant R) does NOT accurately describe the behavior of:

• Non-linear devices such as diodes and transistors
• A simple fixed resistor
• A length of copper wire
• It applies perfectly to every electrical device

Question 21: A 2 kW electric heater runs for 5 hours. How much energy (in kWh) does it use?

• 2 kWh
• 5 kWh
• 10 kWh
• 20 kWh

Question 22: A current of 5 A flows through a 10 Ω resistor. What power is dissipated?

• 50 W
• 150 W
• 250 W
• 500 W

Question 23: A current of 3 A flows through a 20 Ω resistor. What is the voltage across the resistor?

• 6 V
• 23 V
• 60 V
• 600 V

Question 24: Ohm's Law states that voltage equals:

• Current multiplied by resistance (V = I × R)
• Current divided by resistance
• Current plus resistance
• Resistance divided by current

Question 25: A 5 Ω resistor is in series with a parallel combination of two 20 Ω resistors. What is the total circuit resistance?

• 10 ohms
• 15 ohms
• 25 ohms
• 45 ohms