Electricity and Magnetism Answers

The force on a charged proton (charge 1.6 E-19) travelling at 3 E6 m/s through a magnetic field of 4 T is:
(note: E represents power of ten)

A wheel having mass m has charges +q and -q on diametrically opposite points. It remains in equilibrium b on a rough inclined plane in the presence of uniform vertical electric field E

A magnet that is moving towards a 20 turn coil of resistance 12♎ at .5 m/s results in a current of .25A produced in the coil.
What is the force exerted by the coil on the magnet?

A fraction of atoms of radioactive element that decays in 6 days is 7/8 . The fraction that decays in 10 days will be (a). 77/80. (b) 71/80. (c) 31/32. (d) 15/16

If you had an ideal blackbody emitter at 300 degrees kelvin, what wavelength of light (in nanometers) would it emit?

the potential different across the lamp is 4.2v the current in the lamp is then 0.19 a calculate the resistance of the lamp

In the following question, does the mass fall at the rate of gravity?

How much electricity (in kilowatt hours?) Would be produced by a generator / turbine if a 1 tonne weight was suspended from a cable and gravity was pulling it down for 100 meters? Or what would the formula be to solve this?
All potential energy will transform into electricity.
E=mgh=1000*9.8*100=980000 J.
Now we need to express one kilowatt hour in joules: 1 kW*h=1000*3600 W*s=3600000 J.
Now we can express the amount of energy in kWh: E=980000/3600000=0.27 kWh.
Answer: 0.27 kWh.

How much electricity (in kilowatt hours?) Would be produced by a generator / turbine if a 1 tonne weight was suspended from a cable and gravity was pulling it down for 100 meters? Or what would the formula be to solve this?

It is required to hold four equal point charges in equilibrium at the corner of a square. Find the point charge at the centre of the square.

With the decrease of current in the primary coil from 2 ampere to zero value in 0.1 sec , the e.m.f generated in secondary coil is 1000 volts . The mutual inductance of the two coils is (1) 1.25 Henry (2) 2.50 Henry (3) 5.00 Henry (4) 10 Henry