An immersion heater used to boil water for a single cup of tea plugs into a 120 v outlet and is rated at 450 w . suppose your super-size, super-insulated tea mug contains 400 g of water at a temperature of 23 ∘c. you can ignore the energy needed to raise the temperature of the mug and the heater itself. what is the resistance of the heater? how long will this heater take to bring the water to a boil?

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.

What is special about a dc circuit ?

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?