Ow is an electromagnet different from a bar magnet?

question 3 options:

a. only a bar magnet has a magnetic field.

b. only an electromagnet attracts materials made of iron.

c. an electromagnet is temporary and is magnetic when a current flows through a wire wrapped around the core.

d. a bar magnet is a temporary and is only magnetic when a current flows through a wire wrapped around the core.

Name three different units of energy used to measure heat and describe what type of situations each is usually used.

Asteam power plant operates on an ideal reheat rankine cycle between the pressure limits of 15 mpa and 10 kpa. the mass flow rate of steam through the cycle is 12 kg/s. steam enters both stages of the turbine at 500°c. if the moisture content of the steam at the exit of the low-pressure turbine is not to exceed 10 percent, determine (a) the pressure at which reheating takes place, (b) the total rate of heat input in the boiler, and (c) the thermal efficiency of the cycle. also, show the cycle on a t-s diagram with respect to the saturation lines. (2.15 mpa; 45.0 mw; 42.6%)

If it takes a planet 2.8 x 10^8 s to orbit a star with a mass of 6.2 x 10^30 kg what is the average distance between the planet and the star