Ohm law 

Ohm’s Law Quiz MCQs with Answers

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Ohms law quiz is a simple test designed for you to test your knowledge of Ohm’s Law.

1. The statement which correctly represents Ohm’s law:

  1. V = IR
  2. V = R/I
  3. R = VI
  4. I = R/V
    • Correct answer: 1. V = IR

2. A 10 ohms resistor is powered by a 5-V battery. The current flowing through the source is:

  1. 10 A
  2. 50 A
  3. 2 A
  4. 0.5 A
    • Correct answer: 4. 2 A
    • Solution: From I = V/R = 5-V/10 ohm = 0.5 A

3. If V = 50 V and I = 5 A, then R = ___:

  1. 50 Ω
  2. 5 Ω
  3. 10 Ω
  4. 2 Ω
    • Correct answer: 3. 10 Ω
    • Solution: From R = V/I = 50 V/ 5A = 10 Ω

4. If P = 50 watt and R = 2 ohms, then I = ___?

  1. 50 A
  2. 5 A
  3. 10 A
  4. 2 A
    • Correct answer: 3. 5 A
    • Solution: From I = √(P/R) = √(50 V/ 2A) = √25 A = 5 A

5. Unit of voltage is:

  1. Volt
  2. Watt
  3. Coulomb
  4. Ampere
    1. Correct answer: 1. Volt

6. Unit of current is:

  1. Volt
  2. Watt
  3. Coulomb
  4. Ampere
    1. Correct answer: 4. Ampere

7. Unit of power is:

  1. Volt
  2. Watt
  3. Coulomb
  4. Ampere
    1. Correct answer: 2. Watt

8. Unit of resistance is:

  1. Volt
  2. Watt
  3. Ohms
  4. Ampere
    • Correct answer: 3. Ohms

9. If V = 10 V and R = 15 kΩ, then I = ___?

  1. 0.666 mA
  2. 666 µA
  3. 0.66 A
  4. a & b
    • Correct answer: 4. a & b
    • Solution: Here I = V/R = 10 V / 15 kΩ = 0.666 mA = 666 µA

10. If I = 5 A and R = 10 Ω, then P = ___?

  1. 50 watts
  2. 250 watts
  3. 350 watts
  4. 500 watts
    • Correct answer: 2. 250 watt
    • Solution: Here P = I2R = (5 A)2 * 10 Ω = 250 watts

11. Components which obey Ohm’s law are known as:

  1. Resistors
  2. Ohmic components
  3. Non-ohmic components
  4. None of these
    • Correct answer: 2. Ohmic components

12. Ohmic components have a __________ V-I curve:

  1. Straight line VI curve
  2. Parabolic VI curve
  3. Non-linear VI curve
  4. Sinusoidal VI curve
    • Correct answer: 1. Straight line VI curve

Ohms Law Quiz Numerical Problems

13. An electric kettle with 50-Ω heat element is powered by a 230-V wall outlet. The current flowing through kettle is:

  1. 0.217 A
  2. 4.6 A
  3. 10.86 A
  4. 11500 A
    • Correct answer: 2. 4.6 A

14. The water heating rod draws 10 A current when connected to certain power source. The resistance of rod is 12 Ω. The source voltage is:

  1. 1.2 V
  2. 120 V
  3. 1200 V
  4. None of these
    • Correct answer: 2. 120 V

15. A relay with 100 Ω resistance requires 50 mA to for operation. When connected to a 4 V source the relay will:

  1. Operate
  2. Not operate
    • Correct answer: 2. Not operate
    • Solution: At 4 V, the current will I = V/R = 40 mA, which is not enough for the operation

16.The potential difference across a 5 kΩ is 12 V. Find the current flowing through the resistor:

  1. 60 mA
  2. 2.4 mA
  3. 1.77 mA
  4. 0.998 mA
    • Correct answer: 2. 2.4 mA
    • Solution: I = V/R = 12 V / 5 kΩ = 2.4 mA

17. An electrical bulb draws 5 A current when connected to a 100-V wall outlet, the resistance of bulb is:

  1. 5 Ω
  2. 20 Ω
  3. 100 Ω
  4. 500 Ω
    • Correct answer: 2. 20 Ω

18. An unknown resistor has 5 mA current flowing through it when 10 volts are applied to it. For the same resistor, the application of 20 volts will result in the current flow of:

  1. 2 mA
  2. 5 mA
  3. 10 mA
  4. 50 mA
    • Correct answer: 3. 10 mA
    • Solution: Here R = 10 volts / 5 mA = 2  kΩ, Now for 20 volts, I = 20 volts/ 2 kΩ = 10 mA

MCQs involving knowledge of Prefixes in the Ohm law Quiz

Prefixes are numbers which represent the mathematical quantity in the power of ten. We already shared basic of prefixes in Ohm’s law article. In previous sections two prefixes ‘m’ and ‘k’ are introduced. This section of MCQs involves other prefixes as well. Let’s start learning:

19. If I1 = 50 mA, R1 = 50 kΩ, then V1 = __:

  1. 1 kV
  2. 2.5 kV
  3. 5 kV
  4. 10 kV
    • Correct answer: 2. 2.5 kV
    • Hint: 1k = 1000, 1m = 0.001

20. If I2 = 100 µA, R2 = 50 kΩ, then V2 = __:

  1. 5000 V
  2. 500 V
  3. 5 V
  4. 0.5 V
    • Correct answer: 3. 5 V
    • Hint: 1µ = 0.000 001

21. If I3 = 100 µA, R3 = 50 MΩ, then V3 = __:

  1. 5000 V
  2. 500 V
  3. 5 V
  4. 0.5 V
    • Correct answer: 1. 5000 V
    • Hint: 1M = 1 000 000

22. If V4 = 50 V, R4 = 10 GΩ, then I4 = __:

  1. 5 A
  2. 5 mA
  3. 5 µA
  4. 5 nA
    • Correct answer: 4. 5 nA
    • Hint: 1G = 1 000 000 000, 1 n = 0. 000 000 001

23. If V5 = 99 kV, R5 = 33 GΩ, then I5 = __:

  1. 5 A
  2. 5 mA
  3. 5 µA
  4. 5 nA
    • Correct answer: 4. 5 nA

24. If V6 = 22 V, R6 = 11 kΩ, then I6 = __:

  1. 5 A
  2. 5 mA
  3. 5 µA
  4. 5 nA
    • Correct answer: 4. 5 nA
    • Hint: 1G = 1 000 000 000, 1 n = 0. 000 000 001

25. If V7 = 10 V, I7 = 1 μA, then R7 = __:

  1. 10 kΩ
  2. 10 MΩ
  3. 0.1 kΩ
  4. 0.1 MΩ
    • Correct answer: 4. 10 MΩ

27. If V8 = 15 kV, I8 = 2 nA, then R7 = __:

  1. 7500 kΩ
  2. 7500 GΩ
  3. 30 kΩ
  4. 30 GΩ
    • Correct answer: 4. 7500 GΩ

28. If V9 = 50 V, I9 = 25 μA, then R9 = __:

  1. 2 MΩ
  2. 2 GΩ
  3. 1250 MΩ
  4. 1250 GΩ
    • Correct answer: 4. 2 GΩ

Ohm’s law Quiz MCQs with Resistor Color Coding Technique

Color coding technique is used to represent the values of resistors in the form of colored bands. 4, 5 or 6 bands are designed over the bodies of resistors. While 4 band resistors are most commonly available we’ll use them in next problems. The first and second bands represent a number while the third and fourth one represents a multiplier.

29. A resistor is color-coded with four bands, the first one being brown, second, black, third red, and fourth gold. The resistor connects to a 10 V source. Find the current flowing through the resistor.

ohms-law-circuit-with-1k-resistor-and-10-v-source

  1. 1 mA
  2. 10 mA
  3. 100 mA
  4. 1A
    • Correct answer: 2. 10 mA
    • Solution: The resistor can be color coded from the chart as shown below. It is 1k Ohms resistor. Neglecting the tolerance we can easily use the Ohm’s statement I = V/R to find the current.

4-band-resistor-color-coding-chart

30 If 1st band = Yellow; 2nd band = Violet; 3rd band = Brown; and V = 47 V, then I = ___?

  1. 0.1 A
  2. 0.1 mA
  3. 100 mA
  4. 470 mA
    • Correct answer: 1. 0.1 A
    • Solution: From color coding of resistors the resistor is 470 ohms. Now I = V/R = 47/470 = 0.1 A

31. If 1st band = Red; 2nd band = Red; 3rd band = Red; and V = 44 V, then I = ___?

  1. 20 A
  2. 20 mA
  3. 44 A
  4. 44 mA
    • Correct answer: 2. 20 mA
    • Solution: From color coding of resistors the resistor is 2.2 kohms. Now I = V/R = 44/2.2 k = 20 mA

32. If 1st band = Brown; 2nd band = Black; 3rd band = Green; and V = 50 V, then I = ___?

  1. 1 mA
  2. 100 μA
  3. 5 mA
  4. 50 μA
    • Correct answer: 4. 50 μA
    • Here resistance = 1 MΩ

33. If 1st band = Brown; 2nd band = Black; 3rd band = Brown; and I = 50 mA, then by using Ohm law find the value of source voltage:

  1. 0.5 V
  2. 5 V
  3. 50 V
  4. 500 V
    • Correct answer: 2. 5 V
    • Here resistance = 100 ohms

34. If 1st band = Brown; 2nd band = Black; 3rd band = Orange; and I = 50 mA, then by using the formula of Ohm’s law find the value of voltage source which powers the source:

  1. 0.5 V
  2. 5 V
  3. 50 V
  4. 500 V
    • Correct answer: 4. 500 V
    • Here resistance = 10k ohms

35. If 1st band = Orange; 2nd band = Orange; 3rd band = Orange; and I = 10 mA, then by using the formula of Ohm’s law find the value of voltage source which powers the source:

  1. 3 V
  2. 33 V
  3. 330 V
  4. 500 V
    • Correct answer: 3. 330 V
    • Here resistance = 33k ohms

Problems for Series and Parallel Circuits

This portion of quiz involves series circuits. A series circuit contains two or more in which head of the one joins the tail of other and there is no other connection in between them. To solve such circuits simply add the resistors and obtain a single equivalent resistor, then apply the law to find either current or voltage.

36. Two resistors having values 5 ohms and 10 ohms are connected in series to a 10 V source.  Find the current flowing through the circuit:

  1. 0.66 A
  2. 1.5 A
  3. 2 A
  4. 2.5 A
    • Correct answer: 1.5 A
    • Solution: Rtotal = R1 + R2 = 5 ohms + 10 ohms = 15 ohms, Now I = V/Rtotal = 10 V / 15 ohms = 0.66 A

37. Two resistors having values 18 ohms and 50 ohms are connected in series to an unknown source. An ammeter is connected to the circuit which reads 2 A. Find the input voltage to the circuit:

  1. 36 V
  2. 100 V
  3. 136 V
  4. 168 V
    • Correct answer: 136 V
    • Solution: Rtotal = R1 + R2 = 18 ohms + 50 ohms = 68 ohms, Now V = I*Rtotal = 2A * 68 ohms = 136 V

A parallel circuit involves the configuration in which two resistors have their heads joined at common point and tail at another common point. The solution of two or more resistors in parallel follows a simple formula:

Rtotal = 1/((1/R1) + (1/R2))

38. Two parallel resistors both having their values 28 ohms are connected in parallel. The overall current provided by the 28 V source is.

  1. 1 A
  2. 2 A
  3. 4 A
  4. 8 A
    • Correct answer: 2. 2 A
    • Solution: Rtotal = 1/((1/28 Ω) + (1/28 Ω)) = 14 ohms, I = V/R = 28/14 = 2 A

39. Two parallel resistors both having their values 50 and 60 ohms are connected in parallel. The overall current provided by the 100 V source is:

  1. 1.72 A
  2. 2.88 A
  3. 3.66 A
  4. 4.52 A
    • Correct answer: 3. 66 A
    • Solution: Rtotal = 1/((1/50 Ω) + (1/60 Ω)) = 27.27 ohms, I = V/R = 100/27.27 = 3.66 A

40. Repeat the above problem for resistor values of 30 ohms each when the source is 60 V.

  1. 0.25 A
  2. 0.5 A
  3. 2 A
  4. 4 A
    1. Correct answer: 4. 4 A