Physics Quiz - 8/1/23

An electric current i enters and leaves a uniform circular wire of radius a through diametrically opposite points. A charged particle q moving along the axis of the circular wire passes through its centre at speed v. The magnetic force acting on the particle when it passes through the centre has a magnitude:

• Zero

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As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity

• Increases

• Decreases

• Remains constant

• May increase or decrease(Can't be determined)

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Two parallel long wires carry currents i₁ and i₂ with i₁ > i₂. When the currents are in the same direction, the magnetic field at a point midway between the wires is 10T. If the direction of i₂ is reversed, the field becomes 30T. The ratio of i₁ : i₂ is

• 4

• 3

• 2

• 1

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A circular loop of area 1 cm², carrying a current of 10A, is placed in the magnetic field of 0.1 T perpendicular to the plane of the loop. The torque on the loop due to the magnetic field is :

• Zero

• 10^-4 N-m

• 10^-2 N-m

• 1 N-m

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A uniform rod of length l is kept vertically on a horizontal smooth surface at a point O. If it is rotated slightly and released, it falls down on the horizontal surface. The lower end will remain :

• At O

• At a distance less than l/2 from O

• At a distance l/2 from O

• At a distance larger than l/2 from O

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A body having centre of mass at origin has three of its particle at (a,0,0), (0,a,0), (0,0,a). The moments of inertia of the body about X and Y axes are 0.20 kg-m² each. The moment of inertia about the Z-axis :

• Is 0.20 kg-m²

• Is 0.20√2 kg-m²

• Is 0.40 kg-m²

• Cannot be deduced with this information.

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The three vessels shown in the figure have the same base area. Equal volumes of a liquid are poured in the three vessels. The force on the base will be :

• Maximum in vessel A

• Maximum in vessel B

• Maximum in vessel C

• Equal in all the vessels

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An electron is moving along the positive x-axis, You want to apply a magnetic field for a short time so that the electron may reverse its direction and move parallel to the negative x-axis. This can be done by applying the magnetic field along(This is a multiple correct question) :

• y-axis

• z-axis

• y-axis only

• z-axis only

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A sphere is rolled on a rough horizontal surface. It gradually slows down and stops. The force of friction tries to(This is a multiple correct question) :

• Increase the angular velocity

• Decrease the linear velocity

• Increase the linear velocity

• Decrease the angular velocity

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The weight of an empty balloon on a spring balance is W₁. The weight becomes W₂ when the balloon is filled with air. Let the weight of the air itself be w. Neglect the thickness of the balloon when it is filled with air. Also neglect the difference in the densities of air inside and outside the balloon.(This is a multiple correct question) Then :

• W₂ = W₁

• W₂ = W₁ + w

• W₂ < W₁ + w

• W₂ > W₁

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