Physics CH. 25

How is electricity produced?

It all has to do with gaining or losing electrons to create a difference in charge. Like charges repel and unlike charges attract.

Three phase power

Never dead Power lines have four wires and only need 2, bottom wire is the ground wire and other three are live wires that are all different

Explain the process by which power is transmitted from the power generator to your home. Also, explain the advantages of the different stages.

Power plants generate 25,000 volts-creates initial power Transformers then jump it up to 750,000 volts-jumps it up so there will be enough to be distributed It then goes down to substations where it drops to 75,000 volts-step where it gets distributed If then drops down to 5,000 in the country and along highways-Carries it along to the residential areas to the box One it hits residential areas it goes down to 110/120 volts-goes through a breaker box with a safety mechanism so nothing is overloaded

Explain the concept of self-induction

Self-induction is when a coil can induce a voltage in itself and can resist the change in a magnetic field. It can also create a voltage even after the switch is turned off.

What are the two major reasons that explain why alternating current is used in homes?

Since high voltages are more efficient for sending electricity great distances, AC electricity has an advantage over DC. This is because the high voltages from the power station can be easily reduced to a safer voltage for use in the house. Changing voltages is done by the use of a transformer.

What are some advantages of low voltage? What are some advantages of high voltage?

high voltage- large amounts of electricity can be transmitted at relatively low currents. and cheaper because of the smaller cable low voltage-lower power loss in control circuits and safer

Explain the relationships between electricity and magnetism

A change in the electric field induces a change in the magnetic field, A changing magnetic field induces an electric field (Field Induction) when put together, they create light.

In what sense can a transformer be thought of as an electrical lever? What does it multiply? What does it not multiply?

-A transformer can be used to step voltage up or down whenever it is required.-This function is same as the lever. Thus, it is termed an electrical lever. -The transformer multiplies voltage -The transformer does NOT multiply power, i.e. energy/time

What is a transformer and how does it work?

A transformer two coils of wire with an iron core and designed to convert alternating current from one voltage to another. It can be designed to "step up" or "step down" voltages and works on the magnetic induction principle.

Electromagnetic Induction

Changing magnetic field creates an electric field Number of coils determines voltage Used by generators to create alternating current

Why must a transformer use alternating current?

If it didn't have alternating current it would zero

Why can a hum usually be heard when a transformer is operating?

The hum is the same frequency forced vibration of the iron slabs in the transformer core as their magnetic polarities alternate.

Faraday's Law

The induced voltage in a coil is proportional to the product of the number of loops and the rate at which the magnetic field changes within those loops

Suppose you have two almost identical bars with the only difference being that one of them is a magnet. Suppose you drop them down inside of identical copper pipes at the same time. Which will reach the bottom of the copper pipe first?

The one that is not a magnet will reach the bottom of the pipe first because the other will slow down because of the tube acting as a coil heating the tube so it foes from PE to electricity slowing the magnet down.

How could you make a generator?

To make electrical energy, the generator needs a magnetic field and a moving wire to come together. The movement of the wire through the magnetic field is mechanical energy. The force of the two coming together makes the electrons start to flow in the copper wire, thus converting the energy into electricity.

Will a cyclist coast farther if the lamp connected to his generator is turned off?

Yes because it would require less kinetic energy with the light off.