Is electric current a vector or scalar quantity? Explain.

If the electric current is passed through a nerve, the man is excited, why?

A steady current is flowing in a cylindrical conductor. Is there any electric field within the conductor?

How can you keep a constant current inside a conductor?

How does the drift velocity of electrons in a metal conductor vary with the increase in temperature?

If p.d.v applied across a conductor is increased to 2v, how will the draft velocity of the electrons change?

A 10Ω thick wire is stretched so that its length becomes three times. Assuming that there is no change in its density on stretching. Calculate the resistance of new wire

You are given 8 \(\Omega \) resistor. What length of wire of resistance 120 Ωm-1 should be joined in parallel with it to get a value of 6 \(\Omega \) ?

Two wire of equal length one copper and manganin have same resistance , which wire is thicker?

Why manganin is used for making standard resistor?

How is the current conducted in metals? Explain.

If the resistance of our body is so large (\(\approx 10 \ k\Omega\) ) why does one experience a strong shock when one accidently touches the line wire, say a 240 volt supply?

There is an impression among many people that a person touching a high power line gets stuck with the line. Is that true? Explain.

The temperature of the filament of an electric bulb is 2700^oC when it glows. It is not burnt up at such a high temperature. Why?

Three resistance 3Ω, 6Ω and 9Ω are connected to a battery. In which of them will the power dissipation be maximum if
a) They are all connected in parallel
b) They are all connected in series Give reason.

Give any two applications super conductors

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?

Choose the correct alternative:
(a) Alloys of metals usually have (greater/less) resistivity than that of their constituent metals. 
(b) Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.
(c) The resistivity of alloy manganin (is nearly independent of/increases rapidly) with increases of temperature.
(d) The resistivity of a typical insulator (e.g. amber) is greater than that of a metal by a factor of the order of \(\ ({ 10 }^{ 22 }/{ 10 }^{ 23 })\) .

A conductor of length l is connected to a DC source of potential V. If the length of the conductor is tripled by gradually stretching it, keeping V constant, how will
(i) drift speed of electrons and
(ii) resistance of the conductor be affected? Justify your answer

Calculate the conductance and conductivity of a wire of resistance 0.01 \(\Omega\), area of cross-section 10^-4m² and length 0.1 m.

Two cells of voltages 10V and 2V and internal resistances \(10\Omega\ and\ 5\Omega \) respectively are connected in parallel with the positive end of 10V battery connected to negative pole of 2V battery. Find the effective voltage and effective resistance of the combination.

Calculate R_ab in the following circuit:

Four identical cells, each of emf 2V are joined in parallel providing supply of current to external circuit consisting of two 15\(\Omega\) resistors joined in parallel. The terminal voltage of the cells as read by an ideal voltmeter is 1.6V Calculate the internal resistance of each cell.

A 10 m long wire AB of uniform area of cross-section and 20\(\Omega\) resistance is used as a potentiometer wire. This wire is connected in series with a battery of 5V and a resistor o 480\(\Omega\). An unknown e.m.f. is balanced at 600cm of the wire as shown in the figure. Calculate
(i) the potential gradient for the potentiometer wire.
(ii) the value of unknown e.m.f. E.