Current Electricity — practice questions

138 curated practice questions from Current Electricity (Physics Class 12, CBSE) — 74 medium, 55 easy, 9 hard. Every question includes the final answer free; step-by-step worked solutions with a free account.

• The internal resistance of a cell of emf 2 V is 0.1 . It is connected to a resistance of 3.9 . The voltage across the…
• A student measures the terminal potential difference (V) of a cell (of emf and internal resistance r) as a function of…
• Assertion (A): When electrons drift in a conductor, it does not mean that all free electrons in the conductor are…
• In the question number 8, the equivalent resistance between the points A and B , if V A > V B is
• In a dc circuit the direction of current inside the battery and outside the battery respectively are
• The masses of two cylindrical wires of copper are in the ratio of 1 : 3 and their lengths are in the ratio of 5 : 3…
• The voltage of clouds is 4 10 6 V with respect to ground. In a lightning strike lasting 0.1 s, a charge of 4 C is…
• A wire of resistance 10 is elongated by 10%. The resistance of the elongated wire is:
• Assertion (A): When three electric bulbs of power 200 W, 100 W and 50 W are connected in series to a source, the power…
• Which one of the following is the correct representation of variation of conductivity of a conductor with temperature?
• In good conductors of electricity the type of bonding that exist is
• The equivalent resistance of the circuit shown in figure between the points A and B if V A < V B is
• The correct graph showing the variation of the resistance (R) of a cylindrical metal wire as a function of its radius…
• A cell of emf E is connected across an external resistance R. When current I is drawn from the cell, the potential…
• If two identical heaters each rated as (1000 W, 220 V) are connected in parallel to 220 V, then the total power…
• If a wire of resistivity is stretched to double its length, then its new resistivity will:
• In metal with a positive Thomson coefficient, the current is passed from the lower temperature to the high temperature…
• Thermo emf of a thermocouple varies with the temperature of the hot junction as = a + b 2 volt where the ratio ( ab )…
• Assertion (A): The temperature coefficient of resistance is positive for metals and negative for semi-conductors…
• Kirchhoff's first rule I = 0 and second rule IR = E (where the symbols have their usual meanings) are respectively…
• In a uniform straight wire, conduction electrons move along +x direction. Let E and j be the electric field and current…
• Kirchhoff's first and second laws of electrical circuits are consequences of:
• The resistance of a metal wire increases with increasing temperature on account of
• m 2 V -1 s -1 is the SI unit of which of the following?
• The effective resistance between points A and B in the given circuit is:
• A block of pure silicon at 300 K has a length of 10 cm and an area of 1.0 cm 2 . A battery of emf 2 V is connected…
• Charge passing through a conductor of cross-section area A = 0.3 m 2 is given by q = 3t 2 + 5t + 2 in coulomb, where t…
• There are N cells in the circuit of figure. The emf and internal resistance of each cell are and r respectively. The…
• A battery of e.m.f. 12 V and internal resistance 0.5 is connected to a 9.5 resistor through a key. The ratio of…
• The current flowing through a lamp marked as 50 W, 250 V is:
• What length of the wire (specific resistance 48 10 -8 m) is needed to make the resistance of 4.2 ? (Diameter = 0.4 mm)
• Eels are able to generate current with biological cells called electro-plaques. The electro-plaques in an eel are…
• Three copper wires have lengths and cross-sectional areas as (l, A); (2l, A2 ) and ( l2 , 2 A). Resistance is minimum…
• A wire of resistance R, connected to an ideal battery consumes a power P. If the wire is gradually stretched to double…
• Two cells of emf E each and internal resistances r and 2r are connected in parallel as shown in the figure. The…
• A uniform wire of 16 resistance is bent round in the form of a circle. When connected in a circuit between its two…
• A heater coil rated as ( P , V ) is cut into two equal parts. One of the parts is then connected to a battery of V…
• If a current of 1.5 ampere flows through a metallic wire for 3 hours, then how many electrons would flow through the…
• When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the…
• Two conductors A and B of the same material have their lengths in the ratio 1: 2 and radii in the ratio 2: 3 . If they…
• The internal resistance of the primary cell is 4 . It generates a current of 0.2 A in an external resistance of 21 …
• A hot electric iron has a resistance of 80 and is used on a 200 V source. The electrical energy spent, if it is used…
• A conductor of 10 is connected across a 6 V ideal source. The power supplied by the source to the conductor is
• A cell of emf 1.5 V and internal resistance 2 is connected to two resistors of 5 and 8 in series. The potential…
• When the switch of the circuit is turned on, the filament of the bulb glows instantaneously because:
• An electric bulb o f 500 watt at 100 volt is used in a circuit having a 200 V supply. Calculate the resistance R to be…
• The resistance of a wire of length L and radius r is R . Which one of the following would provide a wire of the same…
• Two resistors R 1 and R 2 of 4 and 6 are connected in parallel across a battery. The ratio of power dissipated in them…
• A cell having an emf and internal resistance r is connected across a variable external resistance R. As the resistance…
• Electric field (E) and current density (j) have a relation:
• A wire of resistance 4 is stretched to twice its original length. The resistance of stretched wire would be:
• The potential difference across a cell in an open circuit is 8 V. It falls to 4 V when a current of 4 A is drawn from…
• A battery supplies 0.9 A current through a 2 resistor and 0.3 A current through a 7 resistor when connected one by one…
• Six identical cells, each of emf of 6 V, are connected in parallel. The net emf across the battery is:
• Which of the following is responsible for the flow of current in a conductor?
• If R_ s and R_ p are the equivalent resistances of n resistors, each of value R , in series and parallel combinations…
• A 1250 W heater operates at 115 V. What is the resistance of the heating coil?
• When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the…
• A battery of emf E and internal resistance r is connected to an external circuit. The potential drop within the battery…
• Assertion (A): The equivalent resistance between points A and B in the given network is 2R. Reason (R): All the…
• Two unequal resistors are connected in series across a battery. Then the
• A wire has a resistance of 3.1 at 30° C and a resistance 4.5 at 100 °C. The temperature coefficient of resistance of…
• A light bulb is rated at 100 W for a 220 V ac supply. The resistance of the bulb is
• For a metallic conductor, the correct representation of variation of resistance R with temperature T is:
• Electrons drift with speed v_d in a conductor with potential difference V across its ends. If V is reduced to ( V 2 ) …
• The total power dissipated (in watt) in the circuit shown is
• Three wires A, B and C of the same material have lengths and area of cross-sections as (2 l, ~A 2 ),(l, ~A ) and ( l 2…
• A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it…
• When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the…
• The mean free path of conduction electrons in copper is about 4 × 10 –8 m. The electric field which can give on an…
• Ten identical cells each of emf and internal resistance r are connected in series to form a closed circuit. An ideal…
• The element of a heater is rated (P, V). If it is connected across a source of voltage V 2 , then the power consumed by…
• Kirchhoff s first rule at a junction in an electrical network, deals with conservation of
• When a current of 0.2 A is drawn from a battery, then potential difference between its terminals is 20 V and when a…
• The ratio of masses of three wires is 1 : 2 : 3 and that of their lengths is 3 : 2 : 1. If the wires are made of same…
• Which of the following shows correct range of conductivity? (i) Conductors : 10 4 to 10 7 ohm –1 m –1 (ii) Insulators …
• Mark the incorrect statement. When a potential difference is applied across, the current passing through
• In the network shown in figure, the values of V 0 and I are
• The charge flowing through a resistance R varies with time t as Q = at - bt 2 , where a and b are positive constants…
• A current of 0.8 A flows in a conductor of 40 for 1 minute. The heat produced in the conductor will be
• A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge…
• The conductivity of a metal decreases with the increase in temperature on account of
• Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of…
• The resistance of a wire at a temperature t o C and 0 o C are related by:
• Across a metallic conductor of non-uniform cross-section, a constant potential difference is applied. The quantity…
• If the resistance of the wire is made four times keeping potential difference across it constant, then the number of…
• Nichrome or manganin is widely used in wire-bound standard resistors because of their:
• A cell of constant emf is first connected to a resistance R 1 and then connected to a resistance R 2 . If power…
• The potential difference applied to an X-ray tube is 5 kV and the current through it is 3.2 mA. Then the number of…
• The figure shows the voltage (V) versus the current (I) graphs for a wire at two temperatures T _1 and T _2 . One can…
• The resistivity of the potentiometer wire is 10 -7 m. Its area of cross-section is 10 -6 m 2 . When a current I = 0.1…
• At a hydroelectric power plant the water pressure head is at a height of 300 m and the water flow available is 100 m 3…
• Consider the following two statements: Kirchhoff's junction law follows from the conservation of charge. Kirchhoff's…
• The voltage of clouds is 4 10 6 V with respect to the ground. In a lightning strike lasting 100 m sec, a charge of 4C…
• In a current-carrying conductor, the ratio of the electric field and the current density at a point is called:
• A cell of emf (E) and internal resistance r is connected across a variable external resistance R. The graph of terminal…
• A current of 2 A flows through a 2 resistor when connected across a battery. The same battery supplies a current of 0.5…
• When a current is passed in a conductor, 3°C rise in temperature is observed. If the strength of the current is made…
• Two wires P and Q are made of the same material. The wire Q has twice the diameter and half the length as that of wire…
• Assertion (A): The internal resistance of a cell is constant. Reason (R): Ionic concentration of the electrolyte…
• A student has three resistors, each of resistance R. To obtain a resistance of 2 3 R , she should connect
• On increasing the temperature of a conductor, its resistance increases because the:
• Which pair of readings of ideal voltmeter and ideal ammeter in the given circuit is possible when a suitable power…
• 3 identical bulbs are connected in series and these together dissipate a power P. If now the bulbs are connected in…
• Assertion (A): The given figure does not show a balanced wheatstone bridge. Reason (R): For a balanced bridge small…
• If the length and area of cross-section of a conductor are doubled, then its resistance will be:
• The number of electrons flowing through a conductor per second is 3.3 10 19 . The current flowing through the conductor…
• The ratio of potential difference across AB in the circuit shown for the case (i) when switch S is closed and (ii) when…
• Si and Cu are cooled from 300 K to a temperature of 60 K. Then resistivity:
• The specific resistance of a conductor increases with:
• At 1000°C the resistance of a wire is found to be four times its resistance at 0°C. The temperature coefficient of…
• Four resistors, each of resistance R and a key K are connected as shown in the figure. The equivalent resistance…
• If N is Avogadro number, M is atomic weight and , the density, the number of free electrons per unit volume of a…
• When three identical bulbs of 60-200 volt rating are connected in series to a 200 volt supply, the power drawn by them…
• An electric motor runs on DC source of emf 200 V and draws a current of 10 A. If the Efficiency be 40%, then the…
• Two cells of emf 2 V and 3 V, and internal resistance 1 and 2 , respectively are connected in parallel. The effective…
• Assertion (A): The current density ( J ) at a point in a conducting wire is in the direction of electric field ( E ) at…
• A current flows through a cylindrical conductor of radius R. The current density at a point in the conductor is j = r…
• An electric bulb marked 40 W - 200 V is used in a circuit of supply voltage 100 V. Now its power is:
• Cu and Al wire each of length l = 20 cm and area of cross-section A = 50 cm 2 . Their resistivity _ Cu = 1.69 10 -8 m…
• The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 is:
• The emf and internal resistance of a cell are E and r respectively. It is connected across an external resistance R =…
• Dimension of resistivity (or specific resistance) is:
• A cell of internal resistance r connected across an external resistance R can supply maximum current when
• When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the…
• The current in a device varies with time t as I = 6t, where I is in mA and t is in s. The amount of charge that passes…
• If two identical cells, when connected in series or in parallel, supply the same amount of current through an external…
• A steady current I is passed through a conductor at room temperature for time t. It is observed that its temperature…
• A battery of 16 V and internal resistance 2D is connected to an external resistance R. Find the value of current so…
• The current-voltage graph for a device is shown in the figure. The resistance is negative in the region:
• A steady current of 8 mA flows through a wire. The number of electrons passing through a cross-section of the wire in…
• For a cell, the terminal difference is 2.2 V, when the circuit is open and reduces to 1.8 V, when cell is connected to…
• A potential difference of 200 V is maintained across a conductor of resistance 100 n. The number of electrons passing…
• When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the…
• If the reading of the voltmeter V 1 is 40 V, then the reading of voltmeter V 2 is
• A wire of radius r has resistance R. If it is stretched to the wire of r2 radius, then the resistance becomes:
• The rate of increase of thermo emf with the temperature at the neutral temperature of a thermocouple:
• An electric kettle boils some water in 16 min. Due to some defect, it becomes necessary to remove 10% turns of the…

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