A brass ball is tied to a thin wire and swung so as to move uniformly in a horizontal circle. Which of the following statements in this regard is/are true?

1. The ball moves with constant velocity
2. The ball moves with constant speed
3. The ball moves with constant acceleration
4. The magnitude of the acceleration of the ball is constant

Select the correct answer using the code given below:

• 1 only

• 1 and 3

• 1, 2 and 4

• 2 and 4 only

Two long wires each carrying a d.c. current in the same direction. are placed close to each other. Which one of the following statements is correct?

• The wires will attract each other

• The wires will repel each other

• There will be no force between the wires

• There will be a force between the wires only at the moment when the current is switched ON or OFF

Lightning conductors are used to protect building from lightning strikes. Which of the following statements is/are true about lightning conductors?

1. Lightning conductors create an electric field at its top so that lightning strikes it preferentially
2. Lightning conductors reduce the effect of the strike by uniformly distributing the charge (current) over the surface of the building
3. Lightning conductors take all charge (current) to deep down in the earth
4. Lightning conductors must be installed at a place taller than the building

Select the correct answer using the code given below:

• 1 and 2

• 3 and 4 only

• 1, 3 and 4

• 4 only

174.

In case of a compound microscope which of the following statements is/are correct?

1. The focal length of the eye piece is larger than the focal length of the objective
2. The focal length of the eye piece is smaller than the focal length of the objective
3. The image produced in a normal optical microscope is real
4. The image produced in a normal optical microscope is virtual

Select the correct answer using the code given below:

• 1 only

• 1 and 4

• 2 and 3

• 2 and 4

Which one of the following statements is not correct?

• The radius of curvature of a concave mirror is twice its focal length

• Power of a convex lens is negative and that of a concave lens is positive

• The radius of curvature of a plane mirror is infinity

• When a ray of light passes from an optically denser medium to an optically rarer medium, the angle of refraction is greater than the corresponding angle of incidence

Which one of the following statements is not correct?

• If the velocity and acceleration have opposite sign, the object is slowing down.

• If the velocity is zero at an instant, the acceleration should also be zero at that instant.

• If the velocity is zero for a time interval; the acceleration is zero at any instant within the time interval.

• If the position and velocity have opposite sign, the object is moving towards the origin.

Three equal resistances when combined in series are equivalent to 90 ohm. Their equivalent resistance when combined in parallel will be:

• 10 ohm

• 30 ohm

• 270 ohm

• 810 ohm

The following figure represents the velocity-time graph of a moving car on a road:

Which segment ofthe graph represents the retardation?

• AB

• BC

• CD

• None

A man is sitting in a train which is moving with a velocity of 60 km/hour. His speed with respect to the train is:

• 10/3 m/s

• 60 m/s

• infinite

• zero

Which one of the following is the SI unit ofthe thermal conductivity of a material?

• Wm^-1K^-1

• Wm/K

• Wm^-1/K^-1

• Js^-1m^-1K