Physic 11 - SP

Which of the following electromagnetic radiation is used for viewing objects through fog

• microwave

• gamma rays

• X- rays

• infrared

An oscillator converts

• a.c. power into d.c. power

• d.c. power into a.c. power

• mechanical power into a.c. power

• none of the above

An oscillator produces……………. oscillations

• Damped

• Undamped

• Modulated

• None of the above

An oscillator employs ……………… feedback

• Positive

• Negative

• Neither positive nor negative

• Data insufficient

An LC series circuit with an inductance L and a capacitance C has an oscillation frequency f . Two inductors, each with inductance L , and two capacitors, each with capacitance C , are all wired in series and the circuit is completed. The oscillation frequency is:

• f/4

• f/2

• f

• 2f

A capacitor in an LC oscillator has a maximum potential difference of 15 V and a maximum energy of 360 µJ. At a certain instant the energy in the capacitor is 40 µJ. At that instant what is the potential difference across the capacitor?

• zero

• 5 V

• 10 V

• 15 V

An LC circuit has an inductance of 20 mH and a capacitance of 5 . 0 µF. At time t = 0 the charge on the capacitor is 3 . 0 µC and the current is 7 . 0 mA. The total energy is:

• 4 . 1 × 10^-7 J

• 4 . 9 × 10^-7 J

• 9 . 0 × 10^-7 J

• 1 . 4 × 10^-6 J

An LC circuit has a capacitance of 30 µF and an inductance of 15 mH. At time t = 0 the charge on the capacitor is 10 µC and the current is 20 mA. The maximum charge on the capacitor is:

• 8 . 9 µC

• 10 µC

• 12 µC

• 17 µC

A resistor, an inductor, and a capacitor are connected in parallel to a sinusoidal source of emf. Which of the following is true?

• The currents in all branches are in phase.

• The potential differences across all branches are in phase.

• The current in the capacitor branch leads the current in the inductor branch by one-fourth of a cycle

• The potential difference across the capacitor branch leads the potential difference across the inductor branch by one-fourth of a cycle.

If both the resistance and the inductance in an LR series circuit are doubled the new inductive time constant will be:

• Four times the old

• Half the old

• One-fourth the old

• Unchanged