Important 1 Mark Questions

Important 1 Mark Questions From Board Papers

List of 1 Mark Questions

Q 1. You are asked to measure e.m.f of a cell. Which instrument will you use? A high resistance Voltmeter or Potentiometer and why?
Q 2. An electron and a proton, having equal momenta, enter a uniform magnetic field at right angles to the field lines. What will be the ratio of their trajectories?
Q 3. Why is short wave band used for long distance Radio Broadcast?

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Q 4. If a wire is stretched to double its original length without loss of mass, how will the resistivity of the wire be influenced?
Q 5. When light travel from a rarer to denser medium, the speed decreases. Does this decrease in speed imply a decrease in the energy carried by the light wave? Justify your answer.
Q 6. If the potential difference across a capacitor is doubled, what happens to :
(a) The charge on the capacitor and
(b) The energy stored in the capacitors.
Q 7. Give block diagram of basic units of all communication system.
Q 8. Which of the following 120 V ac device costs more to operate:
(a) One that draws an rms current of 10 A or
(b) One that draws a Peak current of 12 A ?
Q 9.Figure shows a point charge +Q, located at a distance R/2 from the centre of a spherical metal shell. Draw the electric field lines for the given system.
10.Give an example of a material each for which temperature coefficient of resistivity is (i) positive, (ii) negative.

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Q 11.A device "X" is connected to an a.c. source V = Vo sin ωt. The variation of voltage, current and power in one complete cycle is shown in the following figure.
(i) Which curve shows power consumption over a full cycle?
(ii) Identify the device "X".
Q 12.An object is placed in front of convex lens made of glass. How does the image distance vary if the refractive index of the medium is increased in such a way that still it remains less than the glass?
Q 13.Name the network within an institution, made by connecting all or some of their computer.
Q 14.A point charge +Q is placed at point O as shown in the figure. Is the potential difference VA – VB positive, negative or zero ?
Q 15.How does the electric flux due to a point charge enclosed by a spherical Gaussian surface get affected when its radius is increased ?

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Q 16.Write the underlying principle of a moving coil galvanometer.
Q 17.Why are microwaves considered suitable for radar systems used in aircraft navigation ?
Q 18. Define "quality factor" of resonance in series LCR circuit. What is its SI unit ?
Q 19. State Brewster's law.
Q 20.The value of Brewster angle for a transparent medium is different for light of different colours. Give reason.
Q 21.Give one example of use of eddy currents.

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Q 22.Define Electric Flux. Write its SI unit.
Q 23.Depict the behaviour of magnetic field lines in the presence of a diamagnetic material.
Q 24.The charging current for a capacitor is 0.25 A. What is the displacement current across its plates ?
Q 25.Distinguish between polarized and unpolarized light. Does the intensity of polarized light emitted by a polaroid depend on its orientation ? Explain briefly.
Q 26.The vibrations in a beam of polarized light make an angle of 60° with the axis of the polaroid sheet. What percentage of light is transmitted through the sheet ?

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Q 27.In the given figure, charge +Q is placed at the centre of a dotted circle. Work done in taking another charge +q from A to B is W1 and from B to C is W2. Which one of the following is correct: W1 > W2, W1=W2 and W1 < W2?
Q 28.Plot a graph showing the variation of current "I" versus resistance "R", connected to a cell of emf E and internal resistance "r".
Q 29.State the factors on which the refractive index of a material medium for a given wavelength depends.
Q 30.Sketch the emergent wavefront.
Q 31.In the wave picture of light, intensity of light is determined by square of the amplitude of wave. What determines the intensity of light in the photon picture of light?

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Q 32. A flexible wire of irregular shape, abcd, as shown in the figure, turns into a circular shape when placed in a region of magnetic field which is directed normal to the plane of the loop away from the reader. Predict the direction of the induced current in the wire.
Q 33.Why must electrostatic field at the surface of a charged conductor be normal to the surface at every point ? Give reason.
Q 34.Define one tesla using the expression for the magnetic force acting on a particle of charge "q" moving with velocity

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Q 35.In both β and β+ decay processes, the mass number of a nucleus remains same whereas the atomic number Z increases by one in β decay and decreases by one in β+ decay. Explain, giving reason.
Q 36.Arrange the following electromagnetic waves in order of increasing frequency :
γ-rays, microwaves, infrared rays and ultraviolet rays.
Q 37.Figure shows the field lines on a positive charge. Is the work done by the field in moving a small positive charge from Q to P positive or negative ? Give reason
Q 38.The distance from pole of spherical mirror to its focus is called _____________ of that mirror.

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Q 39.A ray of light falls on a transparent sphere with centre C as shown in the figure. The ray emerges from the sphere parallel to the line AB. Find the angle of refraction at A if refractive index of the material of the sphere is √3 .
Q 40.When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the colour of light ?
Q 41.Define dielectric constant of a medium. What is its S.I. unit ?
Q 42.What is the function of a band pass filter used in a modulator for obtaining AM signal ?

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Q 43.A planar loop of rectangular shape is moved within the region of a uniform magnetic field acting perpendicular to its plane. What is the direction and magnitude of the current induced in it ?
Q 44.V – I graph for a metallic wire at two different temperatures T1 and T2 is as shown in the figure. Which of the two temperatures is higher and why ?
Q 45.Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current.
Q 46.To which part of the electromagnetic spectrum does a wave of frequency 5x1019 Hz belong ?
Q 47.Two equal balls having equal positive charge "q" coulombs are suspended by two insulating strings of equal length. What would be the effect on the force when a plastic sheet is inserted between the two ?

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Q 48.Define intensity of radiation on the basis of photon picture of light. Write its S.I. unit.
Q 49.The electric current flowing in a wire in the direction from B to A is decreasing. Find out the direction of the induced current in the metallic loop kept above the wire as shown.
Q 50.Why is it found experimentally difficult to detect neutrinos in nuclear β-decay ?
Q 51.Resolving limit of healthy eye is ___________________.

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Q 52.The frequency of optical waves is of the order of _______________.
Q 53.In a common emitter amplifier , the current gain is 62.The collector resistance and input resistance are 5kΩ and 500 Ω respectively.If the input voltage is 0.01 V , what should be the output voltage?
Q 54.In a double slit experiment , the intensity at a certain point on the screen is 75% of the maximum intensity.What is the phase difference between the waves from the two slits interfering at that point?
Q 55.When the number of turns of the coil in the galvanometer is doubled without changing any other factors, what happens to its
(i) voltage sensitivity
(ii) current sensitivity

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Q 56.The electrostatic force acting between two charges seperated by a distance 'd' is F.At what seperation should the charges be kept so that the force between them is 3F?
Q 57.How is a p-type semiconductor formed?
Q 58.What is the dimension of magnetic flux?
Q 59.The radius of the third Bohr orbit for hydrogen atom is 4.5 A .What is the radius of the fourth Bohr orbit?
Q 60.A 220V , 100W bulb is connected to a source of 180V.What will be the power consumed?

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Q 61.Why is the use of a.c. voltage preferred over d.c. voltage ? Give two reasons.
Q 62.A biconvex lens made of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33. Will the lens behave as a converging or a diverging lens ? Give reason.
Q 63.What do you mean by surface charge density and write its SI unit ?
Q 64.The vertical component of earth's magnetic field at a place is √3 times the horizontal component. What is the angle of dip at this place ?
Q 65.Give two applications of ultra-violet waves.
Q 66.State Ampere's circuital law. Express it mathematically.
Q 67.A wire of resistance 10Ω is stretched to double its length. What will be its new resistance ?
Q 68.State Brewster's law. Express it mathematically.
Q 69.The powers of two lenses are +12D and –2D. They are placed in contact coaxially. What will be the focal length of the combination ?
Q 70.Write full form of "LASER" and "MASER" ?
Q 71.A copper wire and an aluminium wire of the same diameter have their lengths in the ratio 1:2 and their resistivities in the ratio 5:9.Compare their resistances.
Q 72.Name the charge carrier in p-type semiconductor.
Q 73.The drift speed of electrons in a conductor of a circuit is 0.5 mm/s when the potential difference between its end is 1.5V.What will be the drift speed in it when the potential difference across it becomes 3V?
Q 74.Define self inductance of a conducting coil.

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Q 75.Write the unit of electric permittivity in SI system.
Q 76.A pure inductor is connected to a 50Hz a.c source.The instantaneous power in the inductor will have a frequency of ________Hz.
Q 77.Why polarisation is not possible in sound waves?
Q 78.What is amplitude modulation?
Q 79.A convex lens is placed in contact with a plane mirror. A point object at a distance of 20 cm on the axis of this combination has its image coinciding with itself. What is the focal length of the lens?
Q 80.Under what condition does a biconvex lens of glass having a certain refractive index act as a plane glass sheet when immersed in a liquid?
Q 81.If the maximum amplitude of the AM wave is 12V and the minimum amplitude of this wave is 4V, find the modulation index is percentage.
Q 82.What is the function of "moderator" and "Controlling rods" in a nuclear reactor ?
Q 83.Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Name the radiations and write the range of their wavelength.
Q 84.Define the activity of a given radioactive substance. Write its S.I. unit.

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Q 85.Why the core of a transformer is laminated ?
Q 86.What is the lens of Presbyopia and Astingmatism ?
Q 87.What do you mean by conductivity of a material ? Give its SI units.
Q 88.What is Photoelectric effect ? Write Einstein's photoelectric equation.
Q 89.Write the functions of the following in communication system :
(a) Transducer
(b) Repeater
Q 90.Define electric dipole moment and write its SI unit ?
Q 91.Write two characteristics of LASER rays ?

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Q 92.Write logic symbol and truth table of "NOR" gate?
Q 93.Define magnetic flux and write SI unit of magnetic flux ?
Q 94.State Biot-Savart law. Mention its expression ?
Q 95.Define critical angle. State two conditions of total internal reflection of light ?
Q 96.Name the energy losses in a transformer?
Q 97.Define nuclear fission reaction. Mention its nuclear reaction which take place in nuclear reactor ?

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Q 98.Define modulation. Write its types.
Q 99.Calculate the radius of a nucleus of mass no. 8.
Q 100.Write two properties of electric field lines ?
Q 101.If the maximum amplitude of the AM wave is 12V and the minimum amplitude of this wave is 4V, find the modulation index is percentage.
Q 102.What is the function of "moderator" and "Controlling rods" in a nuclear reactor ?

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Q 103.Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Name the radiations and write the range of their wavelength.
Q 104.Define the activity of a given radioactive substance. Write its S.I. unit.
Q 105.Why the core of a transformer is laminated ?
Q 106.What is the lens of Presbyopia and Astingmatism ?
Q 107.What do you mean by conductivity of a material ? Give its SI units
Q 108.What is Photoelectric effect ? Write Einstein's photoelectric equation.

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Q 109.Write the functions of the following in communication system :
(a) Transducer
(b) Repeater
Q 110.Define electric dipole moment and write its SI unit ?
Q 111.Two condensers have capacitances C1 and C2 . Show their parallel combination and series combination circuits.
Q 112. Write Lenz's law of electromagnetic induction.
Q 113. Write any two properties of X-rays.
Q 114.Write any two N-type and P-type semiconductors.

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Q 115.What do you mean by analog and digital signal ?
Q 116.Define current density. Write its SI unit and dimension.
Q 117.State two properties of nuclear force.
Q 118.What is the dl-Brogie wavelength associated with an electron, accelearated through a potential difference of 100 volt.
Q 119.No two electric field lines can intersect each other. Why ?
Q 120. State Gauss's Theorem. Express it mathematically.
Q 121.Differentiate between potentiometer and ordinary voltmeter.

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Q 122.Define inductive reactance (XL). Write its S.I. unit and dimension.
Q 123.A step up transformer is used on a 120V line to provide a potential difference of 2400V. If the primary has 75 turns, how many turns must the secondary have ?
Q 124.State two difference between interference and diffraction.
Q 125.State principle of reversibility of light. Define lateral shift.
Q 126.State superposition principle. Give its one importance.

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Q 127.Mention two factors on which resisitivity depends.
Q 128.Mention different uses of cyclotron.
Q 129.Define power of Lens. Write its S.I. unit.

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Q 130.What are the necessary conditions for obtaining pure spectrum ?
Q 131.Mention applications of Laser technology ?
Q 132.Mention the advantages of "LED" ?
Q 133.State two characters of Couloumb's force.
Q 134.State two properties of equivalential surfaces.

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Q 135.State Ohm's law. Give its mathematical expression.
Q 136.Which of the two has higher resistance : a 1000W heater or a 100 W tungsten bulb, both marked for 230V.
Q 137.Write two uses of a potentiometer.
Q 138.Write two uses of galvanometer.
Q 139.What do you mean by retentivity and coercivity.

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Q 140.Define inductor. Give its symbol.
Q 141.Mention applications of Laser technology ?
Q 142.Mention the advantages of "LED" ?
Q 143.State two characters of Couloumb's force.
Q 144.State two properties of equivalential surfaces.

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Q 145.State Ohm's law. Give its mathematical expression.
Q 146.Which of the two has higher resistance : a 1000W heater or a 100 W tungsten bulb, both marked for 230V.
Q 147.Write two uses of a potentiometer.
Q 148.Write two uses of galvanometer.
Q 149.What do you mean by retentivity and coercivity.

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Q 150.Define inductor. Give its symbol.
Q 151.What is doping ? Why is it dose ?
Q 152.Differentiate between intrinsic semiconductor and extrinsic semiconductors briefly.
Q 153.A TV tower is 80 m tall. Calculate the maximum distance upto which the signal transmitted from the tower can be received.
Q 154.Define Internet. Mention major applications of Internet.
Q 155.Name the spectral series of hydrogen spectrum lying in ultraviolet, infra-red and visible regions ?

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Q 156.Define half life. Mention the relation between half-life and decay constant.
Q 157.Two slits are made 1mm apart and the screen is placed 1 m away. What is the fringe width when bluegreen light of wavelength 500 nm is used ?
Q 158.What are the important uses of polaroids ?
Q 159.Name the principle on which optical fibre works. Mention its two applications.
Q 160.Why does sky appear blue ?
Q 161.State law of Malus?

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Q 162.The half life of a radioactive substance is 20 minutes. The approximate time interval (t2 - t1) between the time t2 when 2/3 of it has decayed and time t1 when 1/3 of it had decayed is ____________.
Q 163.Name the semiconductor device that can be used to regulate an unregulated dc power supply.
Q 164.What happens to the width of depletion layer of a p-n junction when it is (i) forward biased, (ii) reverse biased?
Q 165.Write the functions of three segments of a transistor.
Q 166.Show on a graph, the variation of resistivity with temperature for a typical semiconductor.
Q 167.Name the physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
Q 168.How are infrared waves produced? Why are these referred to as 'heat waves’? Write their one important use.

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Q 169.The permeability of a magnetic material is 0.9983. Name the type of magnetic materials it represents.
Q 170.Where on the surface of Earth is the angle of dip 90°?
Q 171.State Snell's law of refraction of light. Express it mathematically.
Q 172.State two factors by which the range of transmission of TV signal can be increased.
Q 173.A carrier wave of peak voltage 12 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75% ?
Q 174.Write down the Lens maker's formula and what do you mean by spherical aberration of a lens.

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Q 175.Define choke coil. Mention two applications of eddy currents.
Q 176.Express the relationship between commercial unit of energy and S.I. unit of energy. Express the general formula of Joul's heating effect of current.
Q 177.Define Astingmatism. Which lens is used to remove the defect of Astingmatism.
Q 178.The image of a candle is formed on a screen by a convex lens. It half of lens is blackened then what will be the size of image ?
Q 179.What change will occur when a lens is dipped in water ?
Q 180.State properties of photons.

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Q 181. In a parallel plate capacitor with air between the plates, each plates has an area of 6 × 10–3 m2 and the distance between the plates is 3mm. Calculate the capacitance of the capacitor.
Q 182.Define work function and thereshhold frequency related to Einstein's photoelectric effect.
Q 183.State two uses of Photo diode.
Q 184.What is diffraction of light? Write its two kinds.
Q 185.What is self induction? Write its one example.

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Q 186.Write two differences between resistance and specific resistance.
Q 187.Write truth table of OR gate.
Q 188.What is Seeback series? Write its four characteristics.
Q 189.Find the wavelength of photon of 1 eV energy.
Q 190.A bar magnet having pole strength m, magnetic moment m and time period T is divided into two equal parts perpendiculary to length then find its pole strength, magnetic moment and Time period of each part.