In this article, we shared the ohms law objective questions and answers for electrical and electronics engineers.
Ohms Law Objective Questions
The below list provides all the multiple-choice questions related to basics and examples of problems on ohms law.
Answers are available at the bottom of the article.
1. A closed switch has a resistance of
| A) | zero |
| B) | about 50 ohms |
| C) | infinity |
| D) | about 500 ohms |
2. The resistance of a few meters of wire conductor in a closed electrical circuit is
| A) | low |
| B) | practically zero |
| C) | very high |
| D) | high |
3. For which of the following substances the temperature coefficient of resistivity is positive?
| A) | Electrolyte |
| B) | Germanium |
| C) | Carbon |
| D) | Aluminium |
4. Which of the following materials has the least resistivity?
| A) | Zinc |
| B) | Copper |
| C) | Mercury |
| D) | Lead |
5. The resistance of a copper wire 200 m long is 21 ω.
If its thickness (diameter) is 0.44 mm, its specific resistance is around
| A) | 1.2 x 10-8 ω-m |
| B) | 1.4 x 10-8 ω-m |
| C) | 1.8 x 10-8 ω-m |
| D) | 1.6 x 10-8 ω-m |
6. Temperature coefficient of resistance is expressed in terms of
| A) | ohms/ohm°C |
| B) | mhos/ohm°C |
| C) | mhos/°C |
| D) | ohms/°C |
7. Specific resistance of a conductor depends upon
| A) | dimensions of the conductor and composition of conductor material. |
| B) | dimensions of the conductor. |
| C) | composition of conductor material. |
| D) | resistance of the conductor |
8. Heat in a conductor is produced on the passage of electric current due to
| A) | reactance |
| B) | capacitance |
| C) | impedance |
| D) | resistance |
9. Which resistor will be physically larger in size?
| A) | 10ω, 50W |
| B) | 1kω, 1W |
| C) | 1Mω, 1/2W |
| D) | 100ω, 10W |
10. A light bulb draws 300 mA when the voltage across it is 240 V.
The resistance of the light bulb is
| A) | 800 ω |
| B) | 600 ω |
| C) | 400 ω |
| D) | 1000 ω |
11. A 3 ω resistor having 2 A current will dissipate the power of
| A) | 6 watts |
| B) | 8 watts |
| C) | 2 watts |
| D) | 4 watts |
12. With rise in temperature the resistance of semiconductors
| A) | decreases |
| B) | increases |
| C) | remains constant |
| D) | first increases and then decreases |
13. Voltage dependent resistors are usually made from
| A) | graphite |
| B) | charcoal |
| C) | nichrome |
| D) | silicon carbide |
14. For determining the polarity of the voltage drop across a resistor, it is necessary to know the
| A) | value of emf in the circuit. |
| B) | value of current. |
| C) | direction of current flowing through the resistor. |
| D) | value of resistor. |
15. Three resistances of 10 ohms, 15 ohms, and 30 ohms are connected in parallel.
The total resistance of the combination is
| A) | 10 ohms |
| B) | 55 ohms |
| C) | 15 ohms |
| D) | 5 ohms |
16. Which of the following materials possesses the least specific resistance?
| A) | Iron. |
| B) | Aluminium. |
| C) | Silver. |
| D) | Copper. |
17. The temperature coefficient of resistance of an insulator is
| A) | positive and independent of temperature. |
| B) | positive and dependent on temperature |
| C) | negative and dependent on temperature. |
| D) | negative and independent of temperature. |
18. Two resistors R1 and R2 give combined resistance of 4.5 ω when in series and 1 ω when in parallel, the resistances are
| A) | 4 ω and 0.5 ω |
| B) | 1.5 ω and 3 ω |
| C) | 1 ω and 3.5 ω |
| D) | 2 ω and 2.5 ω |
19. Conductance is reciprocal of
| A) | resistance |
| B) | reluctance |
| C) | capacitance |
| D) | inductance |
20. If the length of a wire of resistance R is uniformly stretched to n times its original value, its new resistance is
| A) | n R |
| B) | R/n |
| C) | n2R |
| D) | R/n2 |
21. Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 ω.
If the same four wires are connected is series the effective resistance will be
| A) | 4 ω |
| B) | 2 ω |
| C) | 1 ω |
| D) | 3 ω |
22. Voltage dependent resistors are used
| A) | to supress surges |
| B) | for inductive circuits |
| C) | as heating elements |
| D) | as current stabilizers |
23. The resistance of a parallel circuit consisting of two branches is 12 ohms.
If the resistance of one branch is 18 ohms, what is the resistance of the other?
| A) | 36 ω |
| B) | 64 ω |
| C) | 48 ω |
| D) | 18 ω |
24. In a series circuit with unequal resistances
| A) | the lowest resistance has the highest current |
| B) | In a series circuit with unequal resistances |
| C) | the lowest resistance has the highest voltage drop |
| D) | the highest resistance has the highest voltage drop |
25. Two resistances R1 and R2 are connected in series across the voltage source where R2 > R1. The largest drop will be across
| A) | either R1 or R2 |
| B) | R2 |
| C) | none of these answers |
| D) | R1 |
26. If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes
| A) | 0.4 ohm |
| B) | 1.0 ohm |
| C) | 0.8 ohm |
| D) | 0.6 ohm |
27. A network consists of linear resistors and ideal voltage source.
If the value of the resistors are doubled, then voltage across each resistor is
| A) | not changed. |
| B) | halved. |
| C) | doubled. |
| D) | increased four lines. |
28. The specific resistance of all metals is most affected by
| A) | Degree of illumination |
| B) | Applied magnetic field |
| C) | Temperature |
| D) | Pressure |
29. A resistance having rating 10 ohms, 10 W is likely to be a
| A) | wire wound resistor |
| B) | metallic resistor |
| C) | variable resistor |
| D) | carbon resistor |
30. Four resistances 80 ω, 50 ω, 25 ω and R are connected in parallel.
Current through 25 ω resistance is 4 A.
Total current of the supply is 10 A.
The value of R will be
| A) | 40.25 ω |
| B) | 76.56 ω |
| C) | 66.66 ω |
| D) | 36.36 ω |
31. A rheostat differs from a potentiometer in the respect that it
| A) | has lower wattage rating |
| B) | has higher wattage rating |
| C) | offers large number of tappings |
| D) | has large number of turns |
32. Two resistors are said to be connected in series when
| A) | both carry the same value of current |
| B) | total current equals the sum of branch currents |
| C) | same current passes in turn through both |
| D) | sum of IR drops equals the applied e.m.f. |
33. Which of the following statements is correct regarding resistance?
| A) | The resistance of a conductor is the hindrance by which the conductor opposes the flow of current through it. |
| B) | The resistance of a wire does not depend upon its material. |
| C) | The resistance of wire is independent of the temperature for most of the materials |
| D) | None of these answers |
34. With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals
| A) | 40 W |
| B) | 60 W |
| C) | 10 W |
| D) | 20 W |
35. A thermistor has
| A) | negative temperature coefficient |
| B) | zero temperature coefficient |
| C) | positive temperature coefficient |
| D) | variable temperature coefficient |
36. Specific resistance of a substance is measured in
| A) | ωm2 |
| B) | ω-m |
| C) | m/ω |
| D) | ω/m |
37. The resistance of two wires is 25 ω when connected in series and 6 ω when joined in parallel. The resistance of each wire is
| A) | 10 ω, 15 ω |
| B) | 20 ω, 30 ω |
| C) | 5 ω, 10 ω |
| D) | 10 ω, 20 ω |
38. With rise in temperature the resistance of pure metals
| A) | decreases |
| B) | remains constant |
| C) | increases |
| D) | first increases and then decreases |
39. Resistance of a wire always increases if
| A) | temperature is reduced. |
| B) | number of free electrons available become more. |
| C) | number of free electrons available become less. |
| D) | temperature is increased. |
40. Varistors are
| A) | insulators |
| B) | non-linear resistors |
| C) | carbon resistors |
| D) | resistors with zero temperature coefficient |
41. In equal resistances are first connected in series and then connected in parallel.
What is the ratio of the maximum to the minimum resistance?
| A) | n2 |
| B) | n |
| C) | 1/n |
| D) | 1/n2 |
42. Resistance of material always decreases if
| A) | temperature of material is decreased |
| B) | temperature of material is increased |
| C) | none of these answers |
| D) | number of free electrons available become more |
43. The resistance of a straight conductor does not depend upon its
| A) | Length |
| B) | Material |
| C) | Shape of cross-section |
| D) | Temperature |
44. In a circuit containing two unequal resistors connected in parallel
| A) | The voltage drop is larger across larger resistances |
| B) | The voltage drop is same across both the resistances |
| C) | The current is larger in larger resistance |
| D) | The current is same in both the resistors |
45. The specific resistance of a wire depends upon
| A) | Its dimensions |
| B) | Its length |
| C) | Its cross-sectional area |
| D) | Its material |
46. The temperature coefficient of resistance of a wire is 0.0008°C.
If the resistance of the wire is 8 ohm at 0°C, what is the resistance at 100°C?
| A) | 8.08 Ohm. |
| B) | 7.92 Ohm. |
| C) | 8.64 Ohm. |
| D) | 7.20 Ohm |
47. A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12ohms respectively.
The current in each branch is
| A) | 4.6A,9.6A |
| B) | 6.4 A, 6.9 A |
| C) | 4.6A, 6.9A |
| D) | 6.4 A, 9.6 A |
48. In an ordinary heater if the length of the coil is halved, then a given quantity of water will boil
| A) | More time |
| B) | None of these answers |
| C) | Less time |
| D) | Same time |
49. Twelve 1 ω resistance are used as edges to form a cube.
The resistance between two diagonally opposite corners of the cube is
| A) | 6/5 ω |
| B) | 1 ω |
| C) | 5/6 ω |
| D) | 3/2 ω |
50. Which of the following is an ohmic conductor?
| A) | Thermionic valves |
| B) | Constanton |
| C) | Electrolyte |
| D) | Transistors |
51. Which of the following quantities remain the same in all parts of a series circuit?
| A) | Resistance |
| B) | Current |
| C) | Voltage |
| D) | Power |
52. You have to replace 1500 ω resistor in radio. You have no 1500 ω resistor but have several 1000 ω ones which you would connect
| A) | two in parallel and one in series |
| B) | three in parallel |
| C) | three in series |
| D) | two in parallel |
53. An open resistor, when checked with an ohm-meter reads
| A) | high but within tolerance |
| B) | zero |
| C) | low but not zero |
| D) | infinite |
54. Two copper conductors have equal length.
The cross-sectional area of one conductor is four times that of the other.
If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductors will be
| A) | 20 ohms |
| B) | 160 ohms |
| C) | 80 ohms |
| D) | 10 ohms |
55. The insulation resistance of a cable of length 10 km is 1 Mega Ohm’s.
For a length of 100 km of same cable, the insulation resistance will be
| A) | 1 Mega Ohm |
| B) | 0.1 Mega Ohm |
| C) | 10 Mega Ohm |
| D) | 0.01 Mega Ohm |
56. The temperature coefficient of resistance of some material is negative. The material is
| A) | Germanium |
| B) | Iron |
| C) | Aluminium |
| D) | Copper |
57. The temperature coefficient of resistance of conductors is
| A) | Neutral |
| B) | Negative |
| C) | none of these answers |
| D) | Positive |
58. Three resistances each of R Ω are corrected to form a triangle. The resistance between any two terminals will be
| A) | 3/2 R Ω |
| B) | 3 R Ω |
| C) | 2/3 R Ω |
| D) | R Ω |
59. In a circuit a 33 ω resistor carries a current of 2 A. The voltage across the resistor is
| A) | 66V |
| B) | 132V |
| C) | 33V |
| D) | 80 V |
60. The example of non-ohmic resistance is
| A) | Carbon resistance |
| B) | Copper wire |
| C) | Diode |
| D) | Tungsten wire |
61. Reciprocal of specific resistance is
| A) | Conductive resistance |
| B) | Specific conductance |
| C) | Plate resistance |
| D) | Conductive reactance |
62. The resistance of a conductor varies inversely as
| A) | temperature |
| B) | resistivity |
| C) | area of cross-section |
| D) | length |
63. How are 500 ω resistors connected so as to give an effective resistance of 750ω?
| A) | Three resistors of 500 ω each, in series. |
| B) | Two resistors of 500 ω each, in parallel and the combination in series with another 500 ω resistor. |
| C) | Three resistors of 500 ω each, in parallel |
| D) | Two resistors of 500 ω each, in parallel. |
64. Three parallel resistive branches are connected across a dc supply.
What will be the ratio of the branch currents I1 : I2 : I3 if the branch resistances are in the ratio R1 : R2 : R3 : : 2 : 4 : 6 ?
| A) | 2 : 4 : 6 |
| B) | 3 : 2 : 6 |
| C) | 6 : 2 : 4 |
| D) | 6 : 3 : 2 |
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