A transformer is used to light a lamp rated 40w, 240v from a 400v A. C supply. Calculate: A. The ratio of the number of turns of the primary to the secondary coil.
B. Current drawn from the main circuit if the efficiency of the transformer is 90%.

Aplayground slide is 8.80 ft long and makes an angle of 25.0° with the horizontal. a 63.0-kg child, initially at the top, slides all the way down to the bottom of the slide. (a) choosing the bottom of the slide as the reference configuration, what is the system's potential energy when the child is at the top and at the bottom of the slide? what is the change in potential energy as the child slides from the top to the bottom of the slide? (include the sign of the value in your answer.)