Physics : explain the mechanism by which ac (alternating current) through the primary circuit of a transformer produces an alternating voltage and current in the secondary coil. then explain why this would or would not work with dc (nonalternating current) in the primary coil.

As per Faraday's law of electromagnetic induction we know that when magnetic flux linked with a closed loop will change with time then it will induce EMF in the coil.

Induced EMF is given by the equation

now when AC is connected to the primary coil of a transformer then it will produce magnetic field which is changing with time. This magnetic field is linked with the turns of secondary coil and the flux is produced in it.

Since magnetic field is changing with time due to primary coil so here the flux linked with secondary coil also changes with time and this will induce EMF in secondary coil as per above equation.

Now if we use DC in primary coil then flux linked with secondary coil will be constant and this will not induce any EMF in secondary coil.

So this will work only with AC and not work with DC

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

conservation of mass

mass before something happens = mass afterwards