Electromagnetic induction is the production of a voltage across a conductor when it is exposed to a varying magnetic field. This process is essential in which of these devices?
A) A diode.
B) A capacitor.
C) A transformer
D) A potentiometer.

C) A transformer

Explanation:

Transformers rely on alternating current to induce a current in a secondary coil from a primary coil without them being connected - this voltage is stepped up or down depending on the ratio of turns in each of their coils.

f=ma newton's second law 7x8=56n

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.