1) What is meant by Ohm’s law?
Ohm’s law defines that the current across a conductor between two given points is directly proportional to the voltage between the two points.
V/I = constant
2) What is meant by specific resistance or resistivity?
Specific resistance or resistivity is the resistance of one-metre length wire and the cross-sectional area m2.
3) What is the difference between potential difference and emf?
The potential difference is the work done in displacing a unit charge from one point to another. Emf is the potential difference among the terminals of a cell when no current is extracted from it.
4) Why is a connecting wire thick and enveloped with cotton thread?
Thick copper wires only possess negligible resistance, and covering them with cotton helps to avoid short-circuiting.
5) What is the SI unit of resistivity?
Ohm-metre or Ωm is the SI unit resistivity.
6) What is the wire material used in a rheostat?
Constantan or manganin is the material of wire used in a rheostat.
7) How can we convert a galvanometer into (a) voltmeter (b) ammeter?
(a) By linking a high resistance in series.
(b) By linking a low resistance in parallel.
8) What is the influence of temperature on resistance?
Wire resistance increases with temperature.
9) Can we consider Ohm’s law as a universal law?
No, Ohm’s law is not a universal law. It totally fails on semiconductor materials and for resistances at extremely low temperatures.
10) What happens when the voltmeter is linked in series in a circuit?
A voltmeter is a device used for measuring the potential difference across two points. So, the voltmeter is linked between the two points. Furthermore, the voltmeter has a high resistance, and therefore, the current in the circuit is drastically reduced.
11) What is meant by superconductivity?
In specific materials, the resistance completely vanishes below a distinct temperature. This is called superconductivity.
Also Read:
- To find the resistance of a given wire using a metre bridge and hence determine the resistivity (specific resistance) of its material.
- Chapter Wise Physics Class 12 MCQs
- Physics Class 12 Practicals list
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