Sometimes in physics questions we see examples in which applied force is balanced by an innate force of the body. Like in torsion balances and Cavendish's experiment. In this case we say that rotation( of coil) was up to the point where our applied force balanced the innate restoring force & there is no oscillation in this case. But in certain cases we see that instead of rotation & then stopping the coil rotates. For eg: in a ballistic galvanometer.
So why in similar cases there is rotation in one case & oscillation in other cases ? What causes oscillation in not just the case of a B.G but other things also ( please give other eg also) & what causes just rotation & no oscillation in other one (please give other eg also) ?
Consider the example of an ammeter , the coil rotates till the external torque ( due to current) equals the torsion couple. But in a B.G the coil oscillates though charge ( or current has passed). It doesn't stop the cases are similar but results are different.