Physics Self-Test - Page 13
93- The unit of relative permeability is _________
- (a) henry/metre
- (b) henry
- (c) henry/sq. m
- (d) it is dimensionless
Explanation: Relative permeability ($\mu_r$) is the ratio of the permeability of a specific medium to that of free space ($\mu/\mu_0$). Because it is a ratio of identical dimensions, it evaluates as a dimensionless scalar constant.
94- The working of a meter is based on the use of a permanent magnet. In order to protect the meter functioning from stray magnetic fields:
- (a) meter is surrounded by strong magnetic fields
- (b) a soft iron shielding is used
- (c) a plastic shielding is provided
- (d) a shielding of non-magnetic material is used
Explanation: Soft iron features high magnetic permeability, allowing it to easily channel and redirect external stray magnetic flux lines through its own path layout, effectively shielding internal meter mechanisms inside the enclosure.
100- The process in which a region is made free from any electric field is known as _________
- a. Electrostatic forcing
- b. Electrostatic binding
- c. Electrostatic shielding
- d. None of the options
Explanation: Based on Faraday's cage principle, the electric field inside a hollow conductor equals zero regardless of external fields. This specific isolation strategy is termed electrostatic shielding.
101- The work done in moving a unit positive test charge over a closed path in an electric field is _________
- a. Always 1
- b. Infinite
- c. Zero
- d. Negative
Explanation: The electrostatic field is highly conservative in nature. Consequently, the line integral of the electric field vector along any closed loop path evaluates identically to zero ($\oint E \cdot dl = 0$).
102- A surface that has the same electrostatic potential at every point on it is known as _________
- a. Equal-potential surface
- b. Same potential surface
- c. Equi-magnitude surface
- d. Equipotential surface