Physics Questions and Answers – Ohm’s Law

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This set of Physics Multiple Choice Questions & Answers (MCQs) focuses on “Ohm’s Law”.

1. Give the SI unit of resistivity.
a) ohm/metre2
b) ohm metre2
c) ohm metre
d) ohm/metre
View Answer

Answer: c
Explanation: Resistivity = \(\frac {(Resistance \, \times \, Area)}{Length}\)
SI unit of resistivity=\(\frac {(ohm \, \times \, metre^2)}{metre}\)
= ohm metre.
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2. What is the reciprocal of resistivity of a material called? Give its unit.
a) Conductance, ohm-1
b) Conductivity, ohm-1 m-1
c) Conductance, ohm-1 m-1
d) Conductivity, ohm-1
View Answer

Answer: b
Explanation: Conductivity = \(\frac {1}{Resistivity}\)
SI unit of conductivity = \(\frac {1}{ohm \, meter}\)
= ohm-1 m-1.

3. Give the SI unit of current density and its dimensional formula.
a) Am-2, [A1L-2]
b) Am2, [A1L2]
c) Am-1, [A1L-1]
d) Am1, [A1L1]
View Answer

Answer: a
Explanation: Current density is the amount of charge flowing per second through a unit area.
The SI unit of current density is ampere per square metre (Am-2) and its dimensions are [A1L-2].
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4. Identify the factor which does not depend on the resistance of a conductor.
a) Nature of material
b) Area of cross-section
c) Length
d) Viscosity
View Answer

Answer: d
Explanation: The resistance of a conductor is directly proportional to its length, inversely proportional to the area of cross-section, and nature of the material. The resistance of the conductor does not depend on viscosity.

5. What is the reciprocal of resistance of a material called? Give its unit.
a) Conductance, ohm-1
b) Conductivity, ohm-1 m-1
c) Conductance, ohm-1 m-1
d) Conductivity, ohm-1
View Answer

Answer: a
Explanation: The conductance of a material is the ease with which electric charges flow through it.
Conductance=\(\frac {1}{Resistance}\).
SI unit of conductance=\(\frac {1}{ohm}\)
=ohm-1.
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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter