Current Electricity

A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be

Two sources of equal \(emf\) are connected to an external resistance \(R.\) The internal resistance of the two sources are \({R_1}\) and \({R_2}\left( {{R_1} > {R_1}} \right).\) If the potential difference across the source having interna...

A moving coil galvanometer has \(150\) equal divisions. Its current sensitivity is \(10\)- divisions per milliampere and voltage sensitivity is \(2\) divisions per millivolt. In order that each division reads \(1\) volt, the resistance in $...

The resistance of hot tungsten filament is about \(10\) times the cold resistance. What will be resistance of \(100\) \(W\) and \(200\) \(V\) lamp when not in use ?

In the circuit, the galvanometer \(G\) shows zero deflection. If the batteries \(A\) and \(B\) have negligible internal resistance, the value of the resistor \(R\) will be -

In a potentiometer experiment the balancing with a cell is at length \(240\) \(cm.\) On shunting the cell with a resistance of \(2\Omega ,\) the balancing length becomes \(120\) \(cm\). The internal resistance of the cell is

An energy source will supply a constant current into the load if its internal resistance is

Two voltmeters, one of copper and another of silver, are joined in parallel. When a total charge \(q\) flows through the voltmeters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are \({Z_1}\)...

The total current supplied to the circuit by the battery is

The thermo \(emf\) of a thermocouple varies with temperature \(\theta\) of the hot junction as \(E = a\theta + b{\theta ^2}\) in volts where the ratio \(a/b\) is \({700^ \circ }C.\) If the cold junction is kept at \({0^ \circ }C,\) then ...

The electrochemical equivalent of a metal is \({3.35109^{ - 7}}\) \(kg\) per Coulomb. The mass of the metal liberated at the cathode when a \(3A\) current is passed for \(2\) seconds will be

The Kirchhoff's first law \(\left( {\sum i = 0} \right)\) and second law \(\left( {\sum iR = \sum E} \right),\) where the symbols have their usual meanings, are respectively based on

The resistance of the series combination of two resistances is \(S.\) When they are jointed in parallel the total resistance is \(P.\) If \(S = nP\) then the Minimum possible value of \(n\) is

Thermistors are usually made of

A material \('B'\) has twice the specific resistance of \('A'.\) A circular wire made of \('B'\) has twice the diameter of a wire made of \('A'\). Then for the two wires to have the same resistance, the ratio \({l \over B}/{l \over A}\) of ...

In a meter bridge experiment null point is obtained at \(20\) \(cm\), from one end of the wire when resistance \(X\) is balanced against another resistance \(Y.\) If \(X < Y\), then where will be the new position of the null point from the...

An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the lengths and radii are in the ratio of \({4 \over 3}\) and \({2 \over 3}\), then the ratio of the current passing throu...

An ammeter reads upto \(1\) ampere. Its internal resistance is \(0.81\) \(ohm\). To increase the range to \(10\) \(A\) the value of the required shunt is

The thermo \(e.m.f.\) of a thermo -couple is \(25\) \(\mu V/{}^ \circ C\) at room temperature. A galvanometer of \(40\) \(ohm\) resistance, capable of detecting current as low as \({10^{ - 5}}\,A,\) is connected with the thermo couple. The ...

The length of a wire of a potentiometer is \(100\) \(cm\), and the \(e.\) \(m.\) \(f.\) of its standard cell is \(E\) volt. It is employed to measure the \(e.m.f.\) of a battery whose internal resistance in \(0.5\Omega .\) If the balance po...

A \(3\) volt battery with negligible internal resistance is connected in a circuit as shown in the figure. The current \({\rm I}\), in the circuit will be

The length of a given cylindrical wire is increased by \(100\%\). Due to the consequent decrease in diameter the change in the resistance of the wire will be

The nagative \(Zn\) pole of a Daniell cell, sending a constant current through a circuit, decreases in mass by \(0.13g\) in \(30\) minutes. If the electrochemical equivalent of \(Zn\) and \(Cu\) are \(32.5\) and \(31.5\) respectively, the i...

A \(220\) volt, \(1000\) watt bulb is connected across a \(110\) \(volt\) mains supply. The power consumed will be

If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a

The mass of product liberated on anode in an electrochemical cell depends on (where \(t\) is the time period for which the current is passed).

If \({\theta _1},\) is the inversion temperature, \({\theta _n}\) is the neutral temperature, \({\theta _c}\) is the temperature of the cold junction, then

If in the circuit, power dissipation is \(150W,\) then \(R\) is

A wire when connected to \(220\) \(V\) mains supply has power dissipation \({P_1}.\) Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is \({P_2}.\) Then $${P_2}:{P_...