The diagram shows a piece of pure semiconductor S, in series with a varaible resistor R and a source of constant voltage V. Would you increase or decrease the value of R to keep the reading of ammeter (A) constant, when semiconductor S is heated? Give reason.

A 110 V d.c. heater is used on an a.c. source, such that the heat produced is the same. What would be the r.m.s. value of the alternating voltage?

Direction. In the follwing questions, a statement of assertion is followed by a statement of reason. While answering a question, you are required to choose the correct are out of the given four responses and mark it as (A). If both assertion and reason are true and reason is the correct explanation of the assertion, (B) if both assertion and reason are true but reason is not correct explanation of the assertion. (C) if asssertion is true, but reason if false, (D) if both assertion and reason are false Assertion : The range of an ammeter can be both increased or decreased. Reason : The required shunt resistance can be calculated by using the relation, R= (GS)/(G +S)

The diode used in the circuit shown in the adjacent figure has a constant voltage drop of 0.5V at all currents and a maximum power rating of 100mW.What should be the value of resistor R connected in series with the diode for obtaining maximum current?

Figure 3.33 shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Omega maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 k Omega is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf epsilon and the balance point found similarly, turns out to be at 82.3 cm length of the wire. Would the circuit work well for determining an extremely small emf, say of the order of a few mV (such as the typical emf of a thermo-couple)? If not, how will you modify the circuit?:

In a series RC circuit, R = 30 ohm, C = 0.25 mu F, V = 100 V, omega = 10000 rad//s . Find the current in the circuit and calculate the voltage across the resistor and capacitor. Is the algebraic sum of these voltages more than the source voltage ? If yes, resolve the paradox.