A current of 2 amperes flowing through a conductor produces 80 joules of heat in ten seconds. The resistance of the conductor is:

• 0.5 Ω

• 2 Ω

• 4 Ω

• 20 Ω

A thermoelectric refrigerator works on

• Joule effect

• Seebeck effect

• Peltier's effect

• Thermionic effect

The potential difference between points A and B is:

• 20/7 V

• 40/7 V

• 10/7 V

• zero

A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror, what is the size of the image?

• $\left(\frac{\mathrm{f}}{\mathrm{u} - \mathrm{f}}\right)\mathrm{b}$

• ${\left(\frac{\mathrm{f}}{\mathrm{u} - \mathrm{f}}\right)}^2\mathrm{b}$

• $\left(\frac{\mathrm{f}}{\mathrm{u} - \mathrm{f}}\right){\mathrm{b}}^2$

• $\left(\frac{\mathrm{f}}{\mathrm{u} - \mathrm{f}}\right)$

145.

Find the equivalent resistance between the points A and B :

• 2 Ω

• 4 Ω

• 8 Ω

• 16 Ω

If a current is flowing in a spring, then it:

• compress

• swing

• expand

• remain unaffected

Two bulbs A and B are connected in parallel. Bulb A will glow more than bulb B. If their resistances are R_A and R_B respectively. Then :

• R_A $<$ R_B

• R_A $=$ R_B

• R_A $>$ R_B

• none of these

A resistance of 8 ohm and an inductance of 6 ohm are connected in series to an A.C circuit. The impedence of the circuit is

• 14$\sqrt{2} \mathrm{\Omega }$

• 10 $\mathrm{\Omega }$

• 2$\mathrm{\Omega }$

• 15 $\mathrm{\Omega }$

A battery of 12 volt is charged by a supply of 100 volt as shown in the figure. The charging current is 1.0A. Calculate the value of R

• 45 $\mathrm{\Omega }$

• 105 $\mathrm{\Omega }$

• 88 $\mathrm{\Omega }$

• 95 $\mathrm{\Omega }$

At an instant a positive charge is moving parallel to a current carrying conductor. The path of the positive charge is

• elliptical

• circle

• straight line

• parabola