Practice Questions

Q38.When two tuning forks (fork 1 and fork 2) are sounded simultaneously, 4 beats per second are heard. Now, some tape is attached on the prong of the fork 2 . When the tuning forks are sounded again, 6 beats per seconds are heard. If the frequency of fork 1 is 200 Hz, then what was the original frequency of fork 2 ? (1) 200 Hz (2) 202 Hz (3) 196 Hz (4) 204 Hz

Q39.An observer moves towards a stationary source of sound, with a velocity one fifth of the velocity of sound. What is the percentage increase in the apparent frequency? (1) zero (2) 0.5% (3) 5% (4) 20%

Q40.A charged ball B hangs from a silk thread S which makes an angle θ with a large charged conducting sheet P, as show in the figure. The surface charge density σ of the sheet is proportional to (1) cos θ (2) cot θ (3) sin θ (4) tan θ

Q41.Two point charges +8q and −2q are located at x = 0 and x = L respectively. The location of a point on the x axis at which the net electric field due to these two point charges is zero is (1) 2 L (2) L/4 (3) 8 L (4) 4 L JEE Main 2005 JEE Main Previous Year Paper

Q42.Two thin wires rings each having a radius R are placed at a distance d apart with their axes coinciding. The charges on the two rings are +q and −q . The potential difference between the centres of the two rings is (1) QR/4πε0 d2 (2) − 2πε0 Q [ R1 1 ] √R2+d2 (3) zero (4) − 4πε0 Q [ R1 1 ] √R2+d2

Q43.A fully charged capacitor has a capacitance ' C ' it is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity ' s ' and mass ' m '. If the temperature of the block is raised by ' ΔT '. The potential difference V across the capacitance is (1) (2) mCΔT s √2mCΔTs (3) msΔT (4) c √2msΔTC

Q44.A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C then the resultant capacitance is (1) (n −1)C (2) (n + 1)C (3) C (4) nC

Q45.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 ohms needed to be connected in series with the coil will be (1) 103 (2) 105 (3) 99995 (4) 9995

Q46.Two voltameters one of copper and another of silver, are joined in parallel. When a total charge q flows through the voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are z1 and z2 respectively the charge which flows through the silver voltameter is (1) q z1 (2) q z2 1+ 1+ z2 z1 (3) q z1 (4) q z2 z2 z1

Q47.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 (1) 200Ω (2) 100Ω (3) 500Ω (4) 1000Ω

Q48.Two sources of equal emf are connected to an external resistance R. The internal resistance of the two sources are R1 and R2 (R2 > R1). If the potential difference across the source having internal resistance R2 is zero, then (1) R = R2 × (R1 + R2)/R2 −R1) (2) R = R2 −R1 (3) R = R1R2/ (R1 + R2) (4) R = R1R2/ (R2 −R1) JEE Main 2005 JEE Main Previous Year Paper

Q49.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 (1) doubled (2) four times (3) one fourth (4) halved

Q50.An energy source will supply a constant current into the load of its internal resistance is (1) equal to the resistance of the load. (2) very large as compared to the load resistance. (3) zero. (4) non-zero but less than the resistance of the load.

Q51.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 length becomes 120 cm. The internal resistance of the cell is (1) 1Ω (2) 0.5Ω (3) 4Ω (4) 2Ω

Q52.The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use? (1) 40Ω (2) 20Ω (3) 400Ω (4) 200Ω

Q53.A magnetic needle is kept in a non-uniform magnetic field. It experiences (1) a torque but not a force (2) neither a force nor a torque (3) a force and a torque. (4) a force but not a torque.

Q54.Two thin, long parallel wires separated by a distance 'd' carry a current of 'i' A in the same direction. They will (1) attract each other with a force of μ0i2/(2πd) (2) repel each other with a force of μ0i2/(2πd) (3) attract each other with a force of μ0i2 (2πd2) (4) repel each other with a force of μ0i2 /(2πd2)

Q55.Two concentric coils each of radius equal to 2πcm are placed at right angles to each other. 3 Ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in Weber /m2 at the centre of the coils will be (μ0 = 4π × 10−7 Wb/A-m) (1) 12 × 10−5 (2) 10−5 (3) 5 × 10−5 (4) 7 × 10−5

Q56.A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity then (1) its velocity will decrease. (2) its velocity will increase. (3) it will turn towards right of direction of motion. (4) it will turn towards left of direction of motion

Q57.A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The time taken by the particle to complete one revolution is (1) 2πmq (2) 2πq2B B m (3) 2πqB (4) 2πm m qB

Q58.One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. if each tube moves towards the other at JEE Main 2005 JEE Main Previous Year Paper a constant speed V, then the emf induced in the circuit in terms of B, ℓ and V where ℓ is the width of each tube will be (1) BℓV (2) −BℓV (3) zero (4) 2BℓV

Q59.A coil of inductance 300mH and resistance 2Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in (1) 0.05 s (2) 0.1 s (3) 0.15 s (4) 0.3 s

Q60.The self inductance of the motor of an electric fan is 10H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of (1) C = 4μF (2) C = 8μF (3) C = 1μF (4) C = 2μF

Q61.A circuit has a resistance of 12Ω and an impedance of 15Ω. The power factor of the circuit will be (1) 0.8 (2) 0.4 (3) 1.25 (4) 0.125

Q62.The phase difference between the alternating current and emf is π/2. Which of the following cannot be the constituent of the circuit? (1) C alone (2) R.L (3) L.C (4) L alone