Please help 4~~

2011-02-26 9:23 pm

1. The sinusoidal p.d. V1 is applied across a resistor R produces heat at a mean rate W. What is the mean rate of production of heat when the square-wave p.d. V2 is applied across R?

2. A plane coil of wire containing N turns each of area A is placed so that the plane of the coil makes an angle A with the direction of a uniform magnetic field of flux density B. The coil is now moved through a distance x in time t to the position. What is the e.m.f of the coil?

3. In an X-ray tube, the penetrating power of X-ray beam emitted can be increased by
(1) decreasing the cathode to anode distance while maintaining the same p.d. between them.
(2) raising the temperature of cathode
(3) increasing p.d. between anode and cathode

4. When fission occurs in a heavy nucleus, two nuclei produced
(1) contains equal no. of protons and neutrons
(2) are radioactive
(3) have more binding energy per nucleon than the orginal nucleus.

5. An aluminimum ring hangs vertically from a thread with its axis pointing east-west and it moves anticlockwise. A coil is fixed near to the ring and coaxial with it. It moves anticlockwise also. What is the inittial motion of aluminium ring when the current in the coil is switched on?

回答 (1)

天同

2011-02-27 8:11 pm

✔ 最佳答案

1. The rate of production of heat from a square-wave form of ac is independent of the polarity of the ac voltage.
Hence, power produced on resistor R = (V2)^2/R

2. I suppose there is a diagram associated with the question. How does the coil move, in direction prarllel or perpendicular to the filed lines?The net emf of the coil should be zero if the whole coil remains all the time in the magnetic field.
3. Statement (3) is correct. The max penetrating power of x-ray depends on the x-ray photon energy, which could only be achieved by increasing the cathode-anode voltage.
4. Statement (3) is correct. Heavy radioactive nuclides tend to transform into more stable lighter nuclides through the fission process. Nuclides have higher binding energy per nucleon are more stable.

5. The quetion is unclear. Are the solenoid and coil rotate together? Does the switch turn on during the rotation?

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