Find the energy in KWh consumed in 10 hours by four devices of power 500W each.

Calculate the number of photons emitted in 10 hours by a 60 W sodium lamp ( lambda = 6000Å )

Find the potential energy of a system of four particles each of mass m placed at the vertices of a square of side I .

Find the potential energy of a system of four particles each of mass m place at the vertices of a square fo side l. Also obtain the potential at the centre of the square.

Two resistances 99 ohms and 1 ohm are connected in parallel. Find the current in each when the main current in the circuit is 10 ampere.

Form the pair of linear equations in the following problems and find their solutions (if they exist) by any algebraic method:Places A and B are 100km apart on a highway.One car starts from A and another from B at the same time.If the car travel in the direction at different speeds,they meet in 5 hours.If they travel towared each other,they meet in 1 hour .What are the speeds of the two cars?

The maximum speed of a train is 90 km/h. It takes 10 hours to cover a distance of 500 km. Find the ratio of its average speed to maximum speed?

Which use more energy, a 250 W TV set in 1 hr, or 1200 W toaster in 10 minutes?

A family uses 8 kW of power, (a) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW? (b) Compare this area to that of the roof of a typical house.

Find the radius of circle whose area is equal to the sum of the areas of four other circles of radii 5m,6m,8m and 10m.