Current Electricity

A current of 2 A flows through a 2Ω resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a 9Ω resistor. The internal resistance of the battery is

An electric motor operating on a 60 volt D.C supply draws a current of 10 amp. If the efficiency of the motor is 50%, the resistance of its windings is

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 5-cm and 10 cm from the positive end of the wire in the two cases.The ratio of emfs is

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

In a potentiometer experiment two cells of e.m.f. E₁ and E₂ are used in series and in conjunction and the balancing length is found to be 58 cm of the wire. If the polarity of E₂ is reversed, then the balancing length becomes 29 cm. The ratio of e.m.f. of the two cells E₁/E₂ is

How much work is required to carry a 6 μC charge from the negative terminal to the positive terminal of a 9V battery?

The range of voltmeter is 10 V and its internal resistance is 50Ω. To convert it to a voltmeter of range 15 V, how much resistance is to be added?

Identify the wrong statement

The current flowing through a lamp marked as 50 W and 250 V is

When the rate of flow of charge through a metallic conductor of non-uniform cross-section is uniform, then the quantity that remains constant along the conductor is

Number of electrons in one mC charge, given e = 1.6 x 10⁻¹⁹ C, will be

The resistance of a carbon resistor of colour code Red-Red Green Silver is (in kΩ)

The slope of the graph showing the variation of potential difference V on X-axis and current Y-axis gives conductor

Two wires of equal length and equal diameter and having resistivities ρ₁ and ρ₂ are connected in series. The equivalent resistivity of the combination is

A galvanometer of resistance 50Ω is connected to a battery of 8 V along with a resistance of 3950Ω in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 15 divisions, the resistance in series should be …… Ω

Ohm’s law is not applicable except to

Choose the correct statement

Current flows in semi-conductors through

A metal wire of circular cross-section has a resistance R₁. The wire is now stretched without breaking, so that its length is doubled and the density is assumed to remain the same. If the resistance of the wire now becomes R₂, then R₂:R₁ is

A potentiometer wire of length 100 cm has a resistance of 10Ω. It is connected in series with a resistance and a cell of emf 2V having negligible internal resistance. A source of emf 10 mV is balanced against a length of 40 cm of the potentiometer wire.The value of external resistance is

Which of the following is a vector quantity?

Masses of 3 wires of same metal are in the ratio 1:2:3 and their lengths are in the ratio 3:2:1. The electric resistances are in the ratio

Four identical cells of emf Ԑ and internal resistance r are to be connected in series.Suppose, if one of the cell is connected wrongly, then the equivalent emf and effective internal resistance of the combination is

The resistance of a bulb filament is 100Ω at a temperature of 100⁰C. If its temperature coefficient of resistance be 0.005 per ⁰C, then its resistance will become 200Ω at a temperature

To convert a 800 mV range millivoltmeter of resistance 40Ω into an ammeter of 100 mA range, the resistance to be connected as shunt is

Watt hour meter measures

The dimensions of mobility of charge carriers are

The temperature coefficient of resistance of an alloy used for making resistor is

The e.m.f. of a battery is 2 V and its internal resistance is 0.5 Ω. The maximum power which it can deliver to any external circuit will be

A uniform wire of resistance 9Ω is joined end-to-end to form a circle. Then, the resistance of the circular wire between any two diametrically points is

Dimensional formula for electrical resistance R is given by

The equivalent resistance of two resistors connected in series is 6 Ω and their parallel equivalent resistance is 4/3Ω. What are the values of resistances?

The unit of specific conductivity is

Two identical cells of the same e.m.f. and same internal resistance give the same current through an external resistance of 2 Ω, regardless of whether they are connected in series or in parallel. The internal resistance of the cell is

Four cells, each of emf E and internal resistance r, are connected in series across an external resistance R. By mistake one of the cells is connected in reverse. Then, the current in the external circuit is

The temperature coefficient of a resistance wire is 0.00125 per degree. The resistance at 300 K is 1 Ω. At what temperature its resistance will be 2Ω?

The current in a conductor varies with time t as I=2t+3t² Where I is in amperes and t in seconds. Electric charge flowing through a section of the conductor during t=2 sec to t=3 sec is

Two resistors of resistances 2Ω and 6Ω are connected in parallel. This combination is then connected to a battery of emf 2V and internal resistance 0.5Ω. What is the current flowing through the battery?

Three unequal resistors in parallel are equivalent to a resistance 1 Ω. If two of them are in the ratio 1:2 and if no resistance value is fractional, the largest of the three resistances in ohm is

In Wheatstone bridge, three resistors P,Q and R are conncected in three arms in order and 4th arm of resistance s, is formed by two resistors s₁ and s₂ connected in parallel. The condition for bridge to be balanced is, P/Q

Kirchoff’s I law and II laws of electricity prove respectively the

An electron in potentiometer experiences a force 2.4 x 10⁻¹⁹ N. The length of potentiometer wire is 6m. The emf of the battery connected across the wire is (electronic charge=1.6 x 10⁻¹⁹C)

The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then

In potentiometer experiment, a cell of emf 1.25 V gives balancing length of 30 cm. If the cell is replaced by another cell, then balancing length is found to be 40 cm. What is the emf of second cell?

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

Potentiometer measures the potential difference more accurately than a voltmeter because

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

In India, electricity is supplied for domestic use at 200 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 4 A current flows for 2 min in an electroplating experiment, then m gram of silver is deposited. Then the amount (in gram) of silver deposited by 6 A current flowing for 40 s is

The resistances of the four arms P,Q,R and S in a Wheatstone’s bridge are 10Ω, 30Ω, 30Ωand 90Ω respectively. The emf and internal resistance of the cell are 7V and 5Ω, respectively. If the galvanometer resistance is 50Ω, then the current drawn from the cell will be

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

An electron revolves in a circle at the rate of 10¹⁹ rounds per second. The equivalent current is (e=1.6×10⁻¹⁹C)

A silver wire of radius 0.1 cm carries a current of 2A. If the charge density in silver is 5.86×10²⁸ m⁻³, then the drift velocity is

The electron drift speed is small and the change of the electron is also small but still, we obtain large current in a conductor. This is due

The temperature coefficient of the resistance of a wire is 0.00125 per ⁰C. At 300 K its resistance is 1Ω. The resistance of wire will be 2Ω at

Copper and carbon wires are connected in series and the combined resistor is kept at 0⁰C. Assuming the combined resistance does not vary with temperature, the ratio of the resistances of carbon and copper wires at 0⁰C is (Temperature coefficients of resistivity of copper and carbon respectively are 4 x 10⁻³ /⁰ C and -0.5 x 10⁻³ /⁰ C )

Masses of three wires of copper are in the ratio of 1:3:5 and their lengths are in the ratio of 5:3:1. The ratio of their electrical resistances is

Heat produced in a resistance according to which law?

A steady current is passing through a linear conductor of non-uniform cross-section. The net quantity of charge crossing any cross-section per second is

Which one of the following electrical meter has the smallest resistance?

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

Two wires of the same material having equal area of cross-section have length L and 2L. Their respective resistances are in the ratio

The resistance of an ammeter is 13Ω and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt-resistance is

Two bulbs 60 W and 100 W designed for voltage 220 V are connected in series across 220 V source. The net power dissipated is

A steady current of 1.5 amp flows through a copper voltmeter for 10 minutes. If the electrochemical equivalent of copper is 30 x 10⁻⁵ g coulomb⁻¹, the mass of copper deposited on the electrode will be

The drift speed of electrons in copper wire of diameter and length l is v. If the potential difference across the wire is doubled, then the new drift speed becomes

A potentiometer wire of length 10 m and resistance 10 Ω per metre is connected in series with a resistance box and a 2 volt battery. If a potential difference of 100 mV is balanced across the whole length of potentiometer wire, then the resistance introduced in the resistance will be

If a wire is stretched to four times its length, then the specific resistance of the wire will

Length of a conductor is 50 cm radius of cross section 0.1 cm and resistivity of the conductor = 5 x 10⁻⁵ Ω cm⁻¹. The resistance is

Ohm’s law valid

Two resistors of 6Ω and 9Ω are connected in series to a 120 V source. The power consumed by 6Ω resistor is

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. The value of R is

A student measures the terminal potential difference (V) of a cell (of emf E 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, respectively, equal:

The kirchoff’s first law (∑i=0) and second law (∑iR=∑E), where the symbols have their usual meanings, are respectively based on

When a current of (2.5 ± 0.5) A flows through a wire, it develops a potential difference of (20 ± 1) V, then the resistance of wire is

To draw the maximum current from a combination of cells, how should be the cells be grouped?

Consider the following two statements:
(a) Kirchhoff’s junction law follows from the conservation of charge
(b) Kirchhoff’s loop law follows from the conservation of energy
which is the following is correct?

The resistance of a bulb filament is 100 Ω at a temperature of 100⁰C. If its temperature coefficient of resistance be 0.005 per ⁰C, its resistance will become 200Ω at a temperature of

Two bulbs when connected in parallel to a source take 60W each, the power consumed, when they are connected in series with the same source is

The thermo e.m.f. E in volts of a certain thermocouple is found to vary with temperature difference θ in ⁰C between the two junctions according to the relation
E = 30θ – θ² / 15
The neutral temperature for the thermocouple will be

Two cells when connected in series are balanced on 8m on a potentiometer. If the cells are connected with polarities of one of the cells is reversed, then they balance on 2m. The ratio of emfs of two cells is

The rate of increase of thermo-e.m.f. with temperature at the neutral temperature of a thermocouple

A thermocouple of negligible resistance produces an e.m.f. of 40 µV/⁰C in the linear range of temperature. A galvanometer of resistance 10 ohm whose sensitivity is 1 µA/div, is employed with the thermocouple. The smallest value of temperature difference that can be detected by the system will be

When current I is flowing through a conductor, the drift velocity is v. If the value of current through the conductor and its area of cross-section is doubled, then new drift velocity will be

A wire having resistance 12Ω is bent in the form of an equilateral triangle. The effective resistance between any two corners of the triangle will be

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:

If voltage across a bulb rated 220 V – 100 W drops by 2.5% of its rated value, then the percentage of the rated value by which the power would decrease is

The masses of three wires of copper are in the ratio 1:3:5 and lengths are in the ratio 5:3:1. Then the ratio of their electrical resistance are

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

A voltmeter of range 2 V and resistance 300 Ω cannot be converted into ammeter of range

A wire of resistance 4 ohm is stretched to twice its original length. The resistance of stretched wire would be

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

Charge passing through a conductor of cross-section area A=0.3 m² is given by q=3t²+5t+2 in coulomb, where t is in second. What is the value of drift velocity at t= 2 s?(Given, n=2 x 10²⁵/m³)

The identical cells connected in series are needed to heat a wire of length one meter and radius ‘r’ by 10⁰C 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 time ‘t’?

The drift velocity of the electrons in a copper wire of length 2 m under the application of a potential difference of 200 V is 0.5 ms⁻¹. Their mobility is (in m² V⁻¹ s⁻¹)

When a Daniel cell is connected in the secondary circuit of a potentiometer, the balancing length is found to be 540 cm. If the balancing length becomes 500 cm when the cell is short circuited with 1 Ω, the internal resistance of the cell is

An α-particle and a proton are accelerated through same potential difference from rest. Find the ratio of their final velocity

Two resistances 3Ω and 6Ω are connected in parallel and a 4Ω resistance is connected in series. The current through 3Ω resistance is 0.8 A. Then the potential drop through 4Ω resistance is

If by mistake voltmeter is connected in series and ammeter in parallel then