What is the difference, if any, between appliances with a 2 prong plug and a 3 p…

What is the difference, if any, between appliances with a 2 prong plug and a 3 prong plug?

In the 2 prong system, current travels to the appliance through one prong and leaves through the other prong. The roles of the two prongs interchange every 120th of a second. In the 3-prong system, there is one extra prong and that connects the frame of the appliance to the ground (the earth). This extra connection is a safety feature. If a wire comes loose inside the appliance and touches the frame, the frame can deliver charge and current to you through your hand and you can deliver it to the ground through your feet or your other hand. The earth is very large and a large amount of charge can flow into it without repelling further charge. Moreover most electrical systems are actually connected to the ground at some point. So if current can travel out of the circuit feeding power to the appliance and travel through you and into the ground, it will. You’ll get a shock. The ground connection (the extra prong) allows this extra current to flow to ground so easily that a huge current is drawn out of the power source, causing the fuse or circuit breaker in that power source to break the connection. When that power connection is broken, no power can flow to the appliance at all and you can’t get a shock from it. Plastic appliances often omit the extra prong because they have nothing dangerous to touch on their exteriors.

Can you explain power surges?

Can you explain power surges?

Sometimes lightning strikes a power line and deposits a large amount of charge on it. This charge has considerable electrostatic potential energy so its voltage is very large (a large positive voltage if the lightning carried positive charge, a large negative voltage if the lightning carried negative charge). A the charge flows outward along the wires, it raises the local voltages of the wires. This sudden, brief increase in the local voltages is what you mean by a power surge. Many devices (e.g. computers and televisions) can be damaged by such a surge in voltage. Even a light bulb can be damaged because the extra voltage pushes too much current through the filament and can burn it out.

What is the hum you hear when walking under large power lines?

What is the hum you hear when walking under large power lines?

The electric currents in those lines are reversing 120 times a second in the United States (60 full cycles of reversal, over and back, each second). That means that the electrostatic forces between the charges they carry and anything nearby reverse 120 time a second and the magnetic forces that they exert on one another when currents flow through them turn on and off as well. You hear all of the motions that are caused by the pulsating electric and magnetic forces.