A transformer has 400 turns in its primary winding and 800 turns in its secondary winding. The primary voltage is $$20 \mathrm{~V}$$ and the load in the secondary is 4 ohm. The current in the primary, assuming it to be an ideal transformer, is
An object is placed at a distance of $$12 \mathrm{~cm}$$ from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved $$4 \mathrm{~cm}$$ away from the lens, a real image of the same size as that of the virtual image is formed. The focal length of the lens in $$\mathrm{cm}$$ is
The graph of an object moving with speed v for a time t is shown below.
The graph that shows the distance s travelled by the same object for a time t is




An object of mass $$1 \mathrm{~kg}$$ is allowed to hang tangentially from the rim of the wheel of radius R. When released from the rest, the block falls vertically through $$4 \mathrm{~m}$$ height in 2 seconds. The moment of inertia is $$1 \mathrm{~kg} \mathrm{~m}^2$$. The radius of the wheel $$\mathrm{R}$$ is