Practice Questions

Q36.A long solenoid has 200 turns per cm and carries a current i. The magnetic field at its centre is 6.28 × 10−2 Weber /m2 . Another long solenoid has 100 turns per cm and it carries a current i/3. The value of the magnetic field at its centre is (1) 1.05 × 10−4 Weber/m (2) 1.05 × 10−2 Weber /m2 (3) 1.05 × 10−5Weber/m2 (4) 1.05 × 10−3Weber/m2 JEE Main 2006 JEE Main Previous Year Paper

Q37.In an AC generator, a coil with N turns, all of the same area A and total resistance R, rotates with frequency ω in a magnetic field B. The maximum value of emf generated in the coil is " (1) N.A.B. ω (2) N.A.B.R. ω (3) N.A.B (4) N.A.B.R

Q38.The flux linked with a coil at any instant ' t ' is given by ϕ = 10t2 −50t + 250 The induced emf at t = 3 s is (1) 190 V (2) −190 V (3) −10 V (4) 10 V

Q39.In a series resonant LCR circuit, the voltage across R is 100 volts and R = 1kΩ with C = 2μF. The resonant frequency ω is 200rad/s. At resonance the voltage across L is (1) 4 × 10−3 V (2) 2.5 × 10−2 V (3) 40 V (4) 250 V

Q40.An inductor (L = 100mH), a resistor (R = 100Ω) and a battery (E = 100 V) are initially connected in series as shown in the figure. After a long time the battery is disconnected after short circuiting the points A and B. The current in the circuit 1 mm after the circuit is (1) 1 A (2) 1/eA (3) e A (4) 0.1 A

Q41.The rms value of the electric field of the light coming from the Sun is 720 N/C . The average total energy density of the electromagnetic wave is (1) 3.3 × 10−3 J/m3 (2) 4.58 × 10−6 J/m3 (3) 6.37 × 10−9 J/m3 (4) 81.35 × 10−12 J/m3

Q42.The refractive index of glass is 1.520 for red light and 1.525 for blue light. Let D1 and D2 be an of minimum deviation for red and blue light respectively in a prism of this glass. Then (1) D1 > D2 (2) D1 < D2 (3) D1 = D2 (4) D1 can be less than or greater than depending upon the angle of prism

Q43.The time by a photoelectron to come out after the photon strikes is approximately (1) 10−1 s (2) 10−4 s (3) 10−10 s (4) 10−16 s

Q44.The threshold frequency for a metallic surface corresponds to an energy of 6.2eV , and the stopping potential for a radiation incident on this surface 5 V . The incident radiation lies in JEE Main 2006 JEE Main Previous Year Paper (1) X-ray region (2) ultra-violet region (3) infra-red region (4) visible region

Q45.The anode voltage of a photocell is kept fixed. The wavelength λ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows : (1) (2) (3) (4)

Q46.An alpha nucleus of energy 1 mv2 bombards a heavy nuclear target of charge Ze. Then the distance of closest 2 approach for the alpha nucleus will be proportional to (1) 1 (2) v2 Ze (3) 1 (4) 1 m v4

Q47.The energy spectrum of β-particles [number N(E) as a function of β-energy E ] emitted from a radioactive source is (1) (2) (3) (4)

Q48.When 3Li′ nuclei are bombarded by protons, and the resultant nuclei are 4Be8 , the emitted particles will be JEE Main 2006 JEE Main Previous Year Paper (1) neutrons (2) alpha particles (3) beta particles (4) gamma photons

Q49.A solid which is transparent to visible light and whose conductivity increases with temperature is formed by (1) Metallic binding (2) Ionic binding (3) Covalent binding (4) Van der Waals binding

Q50.The 'rad' is the correct unit used to report the measurement of (1) the rate of decay of radioactive source (2) the ability of a beam of gamma ray photons to produce ions in a target (3) the energy delivered by radiation to a target. (4) the biological effect of radiation

Q51.If the binding energy per nucleon in 73Li and 42He nuclei are 5.60MeV and 7.06MeV respectively, then in the reaction p + 73Li →242He energy of proton must be (1) 39.2MeV (2) 28.24MeV (3) 17.28MeV (4) 1.46MeV

Q52.If the ratio of the concentration of electrons that of holes in a semiconductor is 7 and the ratio of currents is 7 , 5 4 then what is the ratio of their drift velocities? (1) 4 (2) 5 7 8 (3) 4 (4) 5 5 4

Q53.In a common base mode of a transistor, t collector current is 5.488 mA for an emit current of 5.60 mA. The value of the base current amplification factor (β) will be (1) 48 (2) 49 (3) 50 (4) 51

Q54.If the lattice constant of this semiconductor is decreased, then which of the following is correct? (1) All Ec, Eg, Ev decrease (2) All F F−F increase (3) Ec , and Ev increase but Eg decreases (4) Ec , and Ev , decrease Eg increases

Q55.In the following, which one of the diodes is reverse biased? JEE Main 2006 JEE Main Previous Year Paper (1) (2) (3) (4)

Q56.The circuit has two oppositely connect ideal diodes in parallel. What is the current following in the circuit? (1) 1.33 A (2) 1.71 A (3) 2.00 A (4) 2.31 A

Q57.How many moles of magnesium phosphate, Mg3(PO4)2 will contain 0.25 mole of oxygen atoms? (1) 0.02 (2) 3.125 × 10−2 (3) 1.25 × 10−2 (4) 2.5 × 10−2

Q58.Density of a 2.05M solution of acetic acid in water is 1.02 g/mL . The molality of the solution is (1) 1.14 mol kg−1 (2) 2.28 mol kg−1 (3) 3.28 mol kg−1 (4) 0.44 mol kg−1

Q59.According to Bohr's theory, the angular momentum of an electron in 5th orbit is (1) 25 πh (2) 1.0 πh (3) 10 πh (4) 2.5 πh

Q60.In the transformation of 238 92 U to 23492 U , if one emission is an α-particle, what should be the other emission(s)? (1) Two β− (2) Two β− and one β+ (3) One β− and one γ (4) One β+ and one β−