Which of the following conditions must be met to have electric current flow through a circuit?
The circuit must be a closed loop.
The circuit must have a source of electric charges (energy).
A potential difference through the circuit must exist.
All of the above conditions are necessary for electric current flow.

•• al and bert are jogging side-by-side on a trail in the woods at a speed of 0.75 m/s. suddenly al sees the end of the trail 35 m ahead and decides to speed up to reach it. he accelerates at a constant rate of 0.50 m/s2, while bert continues on at a constant speed. (a) how long does it take al to reach the end of the trail? (b) once he reaches the end of the trail, he immediately turns around and heads back along the trail with a constant speed of 0.85 m/s. how long does it take him to meet up with bert? (c) how far are they from the end of the trail when they meet?

If jerome is swinging on a rope and transferring energy from gravitational potential energy to kinetic energy, is being done.

A100-watt light bulb illuminates a solar cell. the electricity from the solar cell operates a water pump that delivers 1 watt of power. what is the efficiency of the system?