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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 12551. |
The first line in the Lyman series has wavelength l. The wavelength of the first line in Balmer series is |
| A. | \[\frac{2}{9}\lambda \] |
| B. | \[\frac{9}{2}\lambda \] |
| C. | \[\frac{5}{27}\lambda \] |
| D. | \[\frac{27}{5}\lambda \] |
| Answer» E. | |
| 12552. |
The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true |
| A. | Its kinetic energy increases and its potential and total energies decrease |
| B. | Its kinetic energy decreases, potential energy increases and its total energy remains the same |
| C. | Its kinetic and total energies decrease and its potential energy increases |
| D. | Its kinetic, potential and total energies decreases |
| Answer» B. Its kinetic energy decreases, potential energy increases and its total energy remains the same | |
| 12553. |
If \[{{\lambda }_{\max }}\] is 6563 \[\overset{\text{o}}{\mathop{\text{A}}}\,\], then wave length of second line for Balmer series will be |
| A. | \[\lambda =\frac{16}{3R}\] |
| B. | \[\lambda =\frac{36}{5R}\] |
| C. | \[\lambda =\frac{4}{3R}\] |
| D. | None of the above |
| Answer» B. \[\lambda =\frac{36}{5R}\] | |
| 12554. |
Every series of hydrogen spectrum has an upper and lower limit in wavelength. The spectral series which has an upper limit of wavelength equal to 18752 \[\overset{\text{o}}{\mathop{\text{A}}}\,\] is |
| A. | Balmer series |
| B. | Lyman series |
| C. | Paschen series |
| D. | Pfund series |
| Answer» D. Pfund series | |
| 12555. |
In the above figure D and E respectively represent |
| A. | Absorption line of Balmer series and the ionization potential of hydrogen |
| B. | Absorption line of Balmer series and the wavelength lesser than lowest of the Lyman series |
| C. | Spectral line of Balmer series and the maximum wavelength of Lyman series |
| D. | Spectral line of Lyman series and the absorption of greater wavelength of limiting value of Paschen series |
| Answer» B. Absorption line of Balmer series and the wavelength lesser than lowest of the Lyman series | |
| 12556. |
Radius of first Bohr orbit is r. What is the radius of 2nd Bohr orbit? |
| A. | 8 |
| B. | 2r |
| C. | 4r |
| D. | \[2\sqrt{2r}\] |
| Answer» D. \[2\sqrt{2r}\] | |
| 12557. |
If the wavelength of the first line of the Balmer series in the hydrogen spectrum is K, then the wavelength of the first line of the Lyman series is |
| A. | \[\left( 27/5 \right)\lambda \] |
| B. | \[\left( 5/27 \right)\lambda \] |
| C. | \[\left( 32/27 \right)\lambda \] |
| D. | \[\left( 27/32 \right)\lambda \] |
| Answer» C. \[\left( 32/27 \right)\lambda \] | |
| 12558. |
A hydrogen atom is in ground state. Then to get six lines in emission spectrum, wavelength of incident radiation should be |
| A. | \[800\overset{\text{o}}{\mathop{\text{A}}}\,\] |
| B. | \[825\overset{\text{o}}{\mathop{\text{A}}}\,\] |
| C. | \[975\overset{\text{o}}{\mathop{\text{A}}}\,\] |
| D. | \[01025\overset{\text{o}}{\mathop{\text{A}}}\,\] |
| Answer» D. \[01025\overset{\text{o}}{\mathop{\text{A}}}\,\] | |
| 12559. |
In a hydrogen like atom electron make transition from an energy level with quantum number n to another with quantum number (n-1). If n>>1, the frequency of radiation emitted is proportional to: |
| A. | \[\frac{1}{n}\] |
| B. | \[\frac{1}{{{n}^{2}}}\] |
| C. | \[\frac{1}{{}^{{{n}^{3}}}/{}_{2}}\] |
| D. | \[\frac{1}{{{n}^{3}}}\] |
| Answer» E. | |
| 12560. |
The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy? |
| A. | I |
| B. | II |
| C. | III |
| D. | IV |
| Answer» D. IV | |
| 12561. |
Suppose potential energy between electron and proton at separation r is given by U= K In (r), where K is a constant. For such a hypothetical hydrogen atom, the ratio of energy difference between energy levels (n=1 and n=2) and (n and n=4) is |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| 12562. |
Which of the following transitions in hydrogen atoms emit photons of highest frequency? |
| A. | n=1 to n=2 |
| B. | n=2 to n=6 |
| C. | n=6 to n=2 |
| D. | n=2 to n=l |
| Answer» E. | |
| 12563. |
An unknown hot gas emits radiation of wavelengths 46.0 nm, 82.8 nm and 103.5 nm only. Assume that the atoms have only two excited states and the difference between consecutive energy levels decreases as energy is increased. Taking. the energy of the highest energy state to be zero, find the energies of the ground state and the first excited state. |
| A. | -27eV,-12eV |
| B. | -6eV,-3eV |
| C. | -HeV,-8eV |
| D. | -9eV,-3eV |
| Answer» B. -6eV,-3eV | |
| 12564. |
Suppose an electron is attracted towards the k origin by a force \[\frac{k}{r}\] where A: is a constant and r is the distance of the electron from the origin. By applying Bohr model to this system, the radius of the nth orbital of the electron is found to be \['{{r}_{n}}'\] and the kinetic energy of the electron to be\['{{K}_{n}}'\]. Then winch of the following is true |
| A. | \[{{K}_{n}}\] independent of n, \[{{r}_{n}}\propto n\] |
| B. | \[{{K}_{n}}\propto \frac{1}{n},{{r}_{n}}\propto n\] |
| C. | \[{{K}_{n}}\propto \frac{1}{n},{{r}_{n}}\propto {{n}^{2}}\] |
| D. | \[{{K}_{n}}\propto \frac{1}{{{n}^{2}}},{{r}_{n}}\propto {{n}^{2}}\] |
| Answer» B. \[{{K}_{n}}\propto \frac{1}{n},{{r}_{n}}\propto n\] | |
| 12565. |
An electron in a hydrogen atom makes a transition from first excited state to ground state. The equivalent current due to circulating electron- |
| A. | increases 2 times |
| B. | increases 4 times |
| C. | increases 8 times |
| D. | remains the same |
| Answer» D. remains the same | |
| 12566. |
A generator at a utility company produces 100 A of current at 4000 V. The voltage is stepped up to 2, 40, 000V by a transformer before it is sent on a high voltage transmission line. The current in transmission line is |
| A. | 3.67 A |
| B. | 2.67 A |
| C. | 1.67 A |
| D. | 2.40 A |
| Answer» D. 2.40 A | |
| 12567. |
The primary of a winding transformer has 400 turns while the secondary has 2000 turns. If the power output from the secondary at 1000 V is 12 kW, what is the primary voltage? |
| A. | 200V |
| B. | 300V |
| C. | 400V |
| D. | 500V |
| Answer» B. 300V | |
| 12568. |
An ideal efficient transformer has a primary power input of 10 kW. The secondary current when the transformer is on load is 25 A. If the primary: secondary turns ratio is 8 : 1, then the potential difference applied to the primary coil is |
| A. | \[\frac{{{10}^{4}}\times {{8}^{2}}}{25}V\] |
| B. | \[\frac{{{10}^{4}}\times 8}{25}V\] |
| C. | \[\frac{{{10}^{4}}}{25\times 8}V\] |
| D. | \[\frac{{{10}^{4}}}{25\times {{8}^{2}}}V\] |
| Answer» C. \[\frac{{{10}^{4}}}{25\times 8}V\] | |
| 12569. |
In an LCR circuit as shown below both switches are open initially. Now switch\[{{S}_{1}}\]is closed, \[{{S}_{2}}\] kept open. (q is charge on the capacitor and\[\tau =RC\]is Capacitive time constant). Which of the following statements is correct? |
| A. | At, t=0, q=CV (1-e) |
| B. | At,\[t=\tau \], \[q=CV/2\] |
| C. | At, \[t=2\tau \], \[q=CV(1-{{e}^{-e}})\] |
| D. | At, \[t=2\tau \], \[q=CV(1-{{e}^{-1}})\] |
| Answer» D. At, \[t=2\tau \], \[q=CV(1-{{e}^{-1}})\] | |
| 12570. |
An inductor (L=0.03 H) and a resistor\[(R=0.15k\Omega )\]are connected in series to a battery of 15V emf in a circuit shown below. The key \[{{K}_{1}}\] has been kept closed for a long time. Then at t= 0, \[{{K}_{1}}\] is opened and key \[{{K}_{2}}\], is closed simultaneously. At f = 1 ms, the current in the circuit will be : \[({{e}^{5}}\cong 150)\] |
| A. | 6.7 Ma |
| B. | 0.67 mA |
| C. | 100 mA |
| D. | 67 mA |
| Answer» C. 100 mA | |
| 12571. |
The circuit shown has been operating for a long time. The instant after the switch in the circuit labeled S is opened, what is the voltage across the inductor \[{{V}_{L}}\] and which labeled point (A or B) of the inductor is at a higher potential? Take \[{{R}_{1}}=4.0\,\Omega \], \[{{R}_{2}}=8.0\,\Omega \] and \[L=2.5\,H\]. |
| A. | \[{{V}_{L}}=12V\], point A is at the higher potential |
| B. | \[{{V}_{L}}=12V\], point B is at the higher potential |
| C. | \[{{V}_{L}}=6V\], point A is at the higher potential |
| D. | \[{{V}_{L}}=6V\], point B is at the higher potential |
| Answer» E. | |
| 12572. |
In the LC circuit, the current is in the direction shown and the charges on the capacitor plates have the signs shown. At this time, |
| A. | I is increasing and Q is increasing |
| B. | I is increasing and Q is decreasing |
| C. | I is decreasing and Q is increasing |
| D. | I is decreasing and Q is decreasing |
| Answer» C. I is decreasing and Q is increasing | |
| 12573. |
In a LCR circuit capacitance is changed from C to 1C. For the resonant frequency to remain unchanged, the inductance should be change from L to |
| A. | 4L |
| B. | 2L |
| C. | \[L/2\] |
| D. | \[L/4\] |
| Answer» D. \[L/4\] | |
| 12574. |
Time constant of L-R circuit will be |
| A. | \[\frac{L}{R}\] |
| B. | \[\frac{2L}{R}\] |
| C. | \[\frac{L}{2R}\] |
| D. | None of these |
| Answer» D. None of these | |
| 12575. |
A coil has an inductance of 0.7 henry and is joined in series with a resistance of \[220\,\Omega \]. When the alternating emf of 220 V at 50 Hz is applied to it then the phase through which current lags behind the applied emf and the watt less component of current in the circuit will be respectively |
| A. | \[30{}^\circ ,\text{ }1\text{ }A\] |
| B. | \[45{}^\circ ,\text{ }0.5\text{ }A\] |
| C. | \[60{}^\circ ,\text{ }1.5\text{ }A\] |
| D. | None of these |
| Answer» C. \[60{}^\circ ,\text{ }1.5\text{ }A\] | |
| 12576. |
A capacitor of\[10\,\mu F\]and an inductor of 1 H are joined in series. An ac of 50 Hz is applied to this combination. What is the impedance of the combination? |
| A. | \[\frac{5({{\pi }^{2}}-5)}{\pi }\Omega \] |
| B. | \[\frac{{{10}^{2}}(10-{{\pi }^{2}})}{\pi }\,\Omega \] |
| C. | \[\frac{10({{\pi }^{2}}-5)}{\pi }\,\Omega \] |
| D. | \[\frac{{{5}^{2}}(10-{{\pi }^{2}})}{\pi }\Omega \] |
| Answer» C. \[\frac{10({{\pi }^{2}}-5)}{\pi }\,\Omega \] | |
| 12577. |
A coil of 40 henry inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is |
| A. | 20 seconds |
| B. | 5 seconds |
| C. | 1/5 seconds |
| D. | 40 seconds |
| Answer» C. 1/5 seconds | |
| 12578. |
A small signal voltage\[V(t)={{V}_{0}}\,\sin \,\omega t\]is applied across an ideal capacitor C: |
| A. | Current I (t), lags voltage V (t) by \[90{}^\circ \]. |
| B. | Over a fall cycle the capacitor C does not consume any energy from the voltage source. |
| C. | Current I (t) is in phase with voltage V (t). |
| D. | Current I (t) leads voltage V (t) by \[180{}^\circ \]. |
| Answer» C. Current I (t) is in phase with voltage V (t). | |
| 12579. |
What is the value of inductance L for which the current is maximum in a series LCR circuit with \[C=10\mu F\] and \[\omega =1000{{s}^{-1}}\]? |
| A. | 1 mH |
| B. | cannot be calculated unless R is known |
| C. | 10 mH |
| D. | 100 mH |
| Answer» E. | |
| 12580. |
In given circuit capacitor initially uncharged. Now at t=0 switch S is closed then current given by source at any time t is |
| A. | \[\frac{2}{R}\left( 1-{{e}^{\frac{-2t}{CR}}} \right)\] |
| B. | \[\frac{\varepsilon }{2R}\left( 1+{{e}^{\frac{-2t}{CR}}} \right)\] |
| C. | \[\frac{\varepsilon }{2R}\left( 1-{{e}^{\frac{-2t}{CR}}} \right)\] |
| D. | \[\frac{2\varepsilon }{R}\left( 1-{{e}^{\frac{-2t}{CR}}} \right)\] |
| Answer» C. \[\frac{\varepsilon }{2R}\left( 1-{{e}^{\frac{-2t}{CR}}} \right)\] | |
| 12581. |
Which of the following plots may represent the reactance of a series LC combination [MP PMT 1999] |
| A. | a |
| B. | b |
| C. | c |
| D. | d |
| Answer» E. | |
| 12582. |
In an ac circuit, the instantaneous values of e.m.f. and current are e = 200 sin 314 t volt and\[i=\sin \,\left( 314t+\frac{\pi }{3} \right)\] ampere. The average power consumed in watt is [NCERT 1990; RPMT 1997] |
| A. | 200 |
| B. | 100 |
| C. | 50 |
| D. | 25 |
| Answer» D. 25 | |
| 12583. |
A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit [MNR 1998; JIPMER 2001, 02] |
| A. | 10 A |
| B. | 5 A |
| C. | 33.3 A |
| D. | 3.33 A |
| Answer» E. | |