Current Electricity

A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 ...

The charge flowing through a resistance R varies with time t is Q = at \(-\) bt2, where \(a\) and \(b\) are positive constants. The total heat produced in R is

A potentiometer wire has length 4 m and resistance 8 \(\Omega\). The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2 V, so as to get a potential gradient 1 mV per cm on the wire is

A, B and C are voltmeters of resistance R, 1.5 R and 3R respectively as shown in the figure. When some potential difference is applied between X and Y, the voltmeter readings are VA, VB and VC respectively, Then

Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is

A potentiometer wire of length L and a resistance r are connected in series with a battery of e.m.f. E0 and a resistance r1. An unknown e.m.f. E is balanced at a length \(l\) of the potentiometer wire. The e.m.f. E will be given by

Two metal wires of identical dimensions are connected in series. If \(\sigma\)1 and \(\sigma\)2 are the conductivity of the combination is

A circuit contains an ammeter, a battery of 30 V and a resistance 40.8 ohm all connected in series. If the ammeter has a coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be

Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 \(\Omega\). The power loss in the wire is

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 ...

The resistances in the two arms of the meter bridge are 5 \(\Omega\) and R\(\Omega\) respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6\(l\)1. The resistance R is

Two rods are joined end to end, as shown. Both have a cross-sectional area of 0.01 cm2. Each is 1 meter long. One rod is of copper with a resistivity of 1.7 \(\times\) 10\(-\)6 ohm-centimeter, the other is of iron with a resistivity of 10...

Ten identical cells connected in series are needed to heat a wire of length one meter and radius 'r' by 10oC in time 't'. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in tim...

A 12 cm wire is given a shape of a right angled triangle ABC having sides 3 cm, 4 cm and 5 cm as shown in the figure. The resistance between two ends (AB, BC, CA) of the respective sides are measuread one by one ratio

A wire of resistance 4 \(\Omega\) is stretched to twice its original length. The resistance of stretched wire would be

The resistances of the four arms P, Q, R and S in a Wheatstone's bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 volt and 5 ohm respectively. If the galvanometer resistance is...

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 \(\Omega\) is

If voltage across a bulb rated 220 volt-100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

In the circuit shown the cells A and B have negligible resistances. For VA = 12 V, R1 = 500 \(\Omega\) and R = 100 \(\Omega\) the galvanometer (G) shows no deflection. The value of Vs is

A ring is made of a wire having a resistance R0 = 12 \(\Omega\). Find the points A and B, as shown in the figure, at which a current carrying conductor should be connected so that the resistance R of the sub circuit between these point is ...

A cell having an emf \(\varepsilon\) and internal resistance r is connected across a variable external resistance R. As the resistance R is increased, the plot of potential difference V across R is given by

The power dissipated in the circuit shown in the figure is 30 watts. The value of R is

If power dissipated in the 9 \(\Omega\) resistor in the circuit shown is 36 watt, the potential difference across the 2 \(\Omega\) resistor is

A current of 2 A flows through a 2 \(\Omega\) resistor when connected across a battery a 2 \(\Omega\) resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9 \(\Omega\) resistor. ...

A thermocouple of negligible resistance
produces an e.m.f. of 40 µV/ºC in the linear range
of temperature. A galvanometer of resistance 10
ohm whose sensitivity is 1 µA/division, is
employed with the thermocouple. The smallest
value of temp...

In the circuit shown in the figure, if the potential at point A is taken to be zero, the potential at point B is

Consider the following two statements.
(A)  Kirchoff's junction law follows from the conservation of charge.
(B)  Kirchhoff's loop law follows from the conservation of energy.
Which of the following is correct?

A potentiometer circuit is set up as shown. The potential gradient, across the potentiometer wire, is k volt/cm and the ammeter, present in the circuit, reads 1.0 A when two way key is switched off. The balance points, when the key between ...

The mean free path of electrons in a metal is 4 \(\times\) 10\(-\)8 m. The electric field which can give on an average 2 eV energy to an electron in the metal will be in units V/m

A wire of resistance 12 ohms per meter is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite points, A and B as shown in the figure is

A student measures the terminal potential difference (V) of a cell (of emf \(\varepsilon\) and internal resistance r) as a function of the current (I) flowing through it. The slope, and intercept, of the graph between V and I, then respect...

See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it ?

A wire of a certain material is stretched slowly by ten percent. Its new resistance and specific resistance become respectively

A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively with and without being short circuited through a resistance of 10 \(\Omega\). Its internal resistance is

An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20oC ? The temperature of boiling water is 100oC

A current of 3 amp. flows through the 2 \(\Omega\) resistor shown in the circuit. The power dissipated in the 5 \(\Omega\) resistor is

In the circuit shown, the current through the 4 \(\Omega\) resistor is 1 amp when the points P and M are connected to a d.c. voltage source. The potential difference betwen the points M and N is

The total power dissipated in watt in the circuit shown here is

Three resistances, P, Q, R each of 2\(\Omega\) and an unknown resistance S from the four arms of a Wheatstone bridge circuit. When a resistance of 6 \(\Omega\) is connected in parallel to S the bridge gets balanced. What is the value of S...

Power dissipated across the 8 \(\Omega\) resistor in the circuit shown here is 2 watt. The power dissipated in watt units across the 3 \(\Omega\) resistor is

In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will

Two cells, having the same e.m.f. are connected in series through an external resistance R. Cells have internal resistances r1 and r2 (r1 > r2) respectively. When the circuit is closed, the potential difference across the first cell is zero...

Kirchoff's first and second laws of electrical circuits are consequences of

A 5-ampere fuse wire can withstand a maximum power of 1 watt in the circuit. The resistance of the fuse wire is

For the network shown in the figure the value of the current \(i\) is

When a wire of uniform cross-section \(a\) length \(l\) and resistance R is bent into a complete circle. resistance between any two of diametrically opposite points will be

Two batteries, one of emf 18 volts and internal resistance 2 \(\Omega\) and the other of emf 12 volts and internal resistance 1 \(\Omega\), are connected as shown. The voltmeter V will record a reading of

In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60 W bulb for use in India is R, the resistance of a 60 W bulb for use in USA will be

when three identical bulbs of 60 watt, 200 volt rating are connected in series to a 200 volt supply, the power drawn by them will be

Resistance n, each of r ohm, when connected in parallel give an equivalent resistance of R ohm. If these resistances were connected in series, the combination would have a resistance in ohms, equal to