Figure shows a potentiometer with a cell of 2.0V and internal resistance of 0.40\(\Omega\) maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02V (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 600k\(\Omega\) is put in series with it Which is shorted cell is then replaced by a cell of unknown emf E and the balance point found similarly, turns out to be at 82.3 cm length of the wire.

(a) What is the value E?
(b) What purpose does the high resistance o 600k\(\Omega\) have?
(c) Is the balance point affected by this high resistance?
(d) Is the balance point affected by the internal resistance of 600k\(\Omega\) have?
(e) Would the method work in the above situation if the driver cell of the potentiometer had an emf of 1.0V instead of 2.V?
(f) Would the circuit work well for determining an etremely small emf say of the order of a few mV (such as the typical emf of a thermo-couple)? If not how will you modiy the circuit?

A dc supply of 120V  is connected to a large resistance X. A voltmeter of resistance 10k\(\Omega\)placed in series in the circuit reads 4V. What is the value of X? What so you think is the purpose in using a voltmeter instead of an ammeter to determine the large resistance X?

(a) Three resistors \(1\Omega ,2\Omega \ and\ 3\Omega \) are combined in series. What is the total resistance of the combination?
(b) If the combination is connected to a battery of emf 12 V and negligible internal resistance, obtain the potential drop across each resistor.

(a) Six lead-acid type of secondary cells each of emf 2.0 V and internal resistance are joined in series to provide a supply to a resistance of \(8.5\Omega \) . What are the currents drawn from the supply, and its terminal voltage? (b) A secondary cell after long use has an emf 1.9 V and a large internal resistance of \(380\Omega \). What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?

Answer the following questions:
(a) A steady current flows in a metallic conductor of non-uniform cross-section. Say which of these quantities is constant along the conductor current density, electric field, drift speed?
(b) Is Ohm's law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm's law.
(c) A low voltage supply from which one needs high currents must have very low internal resistance. Why?
(d) A high tension (HT) supply of say 6kV must have a very large internal resistance. Why?

Figure shows a potentiometer circuit for comparison of two resistances.The balance point with a standard resistor \(10.0\Omega \) is found to be 58.3cm while that with the unknown resistance X is 68.5cm. Determine the value of X is 68.5cm. Dtetermine the value of X. What would you do if you failed to find a balance point with the given cell of emf E?

Consider a current carrying wire in the shape of a circle. Note that as the current progresses along the wire, the direction of j changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is
(a) source of e.m.f.
(b) electric field produced by charges accumulated on the surface of wire.
(c) the charges just behind a given segment of wire which push them just the right way by repulsion.
(d) the charges ahead.

Which of the following characteristics of electrons determines the current in a conductor?
(a) Drift velocity alone
(b) Thermal velocity alone
(c) Both drift velocity and thermal velocity
(d) Neither drift nor thermal velocity.

Temperature dependence of resistivity \(\rho (T)\) of semiconductors, insulators and metals is significantly based on the following factors:
(a) number of charge carriers can change with temperature T.
(b) time interval between two successive collisions can depend on T.
(c) length of material can be a function of T.
(d) mass of carriers is a function of T.

What is the advantages of using thick metallic strips to join wires in a potentiometer?

For wiring in the home, one uses Cu wires or Al wires. What considerations are involved in this?

While doing an experiment with potentiometer it was found that the deflection is one sided and
(i) the deflection decreased while moving from one end A of the wire to the end B;
(ii) the deflection increased, while to the end B; (ii) the deflection increased, while the jockey was moved towards the end B.

(i) Which terminal +ve or -ve of the cell \({ E }_{ 1 }\) , is connected at X in case (i) and how is \({ E }_{ 1 }\)related to E?
(ii) Which terminal of the cell \({ E }_{ 1 }\)is connected at X in case(ii)?

A given wire having resistance R is stretched so as to reduce its diameter of half of its previous value. What will be its new resistance?

Three identical cells each of emf 2V and unknown internal resistance are connected in parallel. This combination is connected to a 5-ohm resistor. If the terminal voltage across the cells is 1.5V, what is the internal resistance of each cell?