161.

The equivalent resistance between the points A and B will be (each resistance is 15 Ω)

          

• 30 Ω

• 8 Ω

• 10 Ω

• 40 Ω

Two similar circular loops carry equal currents in the same direction. On moving coils further apart, the electnc current will

• increase in both

• decrease in both

• remain unaltered

• increases in one and decreases in the second

Three resistors 1 Ω, 2 Ω and 3 Ω are connected to form a triangle. Across 3 Ω res1stor a 3 V battery is connected. The current through 3 Ω resistor is

• 0.75 A

• 1 A

• 2 A

• 1.5 A

The accurate measurement of emf can be obtained using

• multimeter

• voltmeter

• voltameter

• potentiometer

The resistance of a wire at 300 K is found to be 0.3 2. If  the temperature coefficient of resistance of wire is 1.5 x 10^-3 K^-1, the temperature at which the resistance becomes 0.6 Ω is

• 720 K

• 345 K

• 993 K

• 690 K

Near a circular loop of conducting wire as shown in the figure an electron moves along a straight line. The direction of the induced current if any in the loop is

• variable

• clockwise

• anti-clockwise

• zero

A battery of emf E has an internal resistance r. A variable resistance R is connected to the terminals of the battery. A current i is drawn from the battery. V is the terminal potential difference. If R alone is gradually reduced to zero, which of the following best describes i and V ?

• i approaches zero, V approaches E

• i approaches $\frac{\mathrm{E}}{\mathrm{r}}$, V approaches zero

• i approaches $\frac{\mathrm{E}}{\mathrm{r}}$, V approaches E

• i approaches infinity, V approaches E

Three voltmeters A, B and C having resistances R, 1.5R and 3R respectively are used in a circuit as shown. When a potential difference is applied between X and Y, the readings of the voltmeters are V₁ and V₂, V₃ respectively. Then

• V₁ = V₂ = V₃

• V₁ < V₂ = V₃

• V₁ > V₂ > V₃

• V₁ > V₂ = V₃

In the circuit given here, the points A, B and C are 70 V, zero, 10 V respectively. Then

• the point D will be at a potential of 60 V

• the point D will be at a potential of 20 V

• currents in the paths AD, DB and DC are in the ratio of 1 : 2 : 3

• currents in the paths AB, DB and DC are in the ratio of 3 : 2 : 1

B₁, B₂ and B₃ are the three identical bulbs connected to a battery of steady emf with key K closed. What happens to the brightness of the bulbs B₁ and B₂ when the key is opened ?

• Brightness of the bulb B₁ increases and that of B₂ decreases

• Brightness of the bulbs B₁ and B₂ increase

• Brightness of the bulb B₁ decreases and B₂ increases

• Brightness of the bulbs B₁ and B₂ decrease