A small current carrying loop acts as a small magnet. The area of the loop is A and magnetic moment is M. The current in the loop will be

• $\frac{\mathrm{A}}{\mathrm{M}}$

• $\frac{\mathrm{M}}{\mathrm{A}}$

• MA

• A²M

The electrical resistivity of a sample

• is proportional to its length

• is proportional to the area of cross-section

• is inversely proportional to the length

• neither depends on the length nor on the area of cross-section

A voltmeter of resistance 998 $\mathrm{\Omega }$ is connected across a cell of emf 2V and internal resistance 2$\mathrm{\Omega }$. The potential difference across the voltmeter is

• 1.99 V

• 3.5 V

• 5 V

• 6 V

A battery of four cells in series,each having an emf of 1 .4 V and an internal resistance of 2 $\mathrm{\Omega }$ is to be used to charge a small 2 V accumulator of negligible internal resistance. What is the charging current?

• 0.1 A

• 0.2 A

• 0.3 A

• 0.45 A

An ammeter reads upto 1 A. Its internal resistance is 0.81 Ω. To increase the range to 10 A, the value of the required shunt is

• 0.03 Ω

• 0.3 Ω

• 0.9 Ω

• 0.09 Ω

The length of a wire of a potentiometer is 100 cm, and the emf of its stand and cell is E volt. It is employed to measure the emf of a battery whose internal resistance is 0.52 Ω.1fthe balance point is obtained at l= 30 cm from the positive end, the emf of the battery is

• $\frac{30\mathrm{E}}{100.5}$

• $\frac{30\mathrm{E}}{100 - 0.5}$

• $\frac{30 (\mathrm{E} - 0.5\mathrm{i})}{100},\mathrm{where} \mathrm{i} \mathrm{is} \mathrm{the} \mathrm{current} \mathrm{in} \mathrm{the} \mathrm{potentiometer} \mathrm{wire}$

• $\frac{30\mathrm{E}}{100}$

The material of wire of potentiometer is made of

• copper

• steel

• manganin

• aluminium

A potential difference V is applied at the ends of a copper wire of length l and diameter d. On doubling only d, drift velocity

• becomes two times

• becomes half

• does not change

• becomes one-fourth

159.

Temperature of a piece of silicon is raised from 27°C to 100°C, then its conductivity

• increases

• decreases

• remains same

• becomes zero

Work of invertor is

• to change AC into DC

• to change DC into AC

• to regulate voltage

• None of the above