1. Back to indicates return.

Pattern 1: verb + back to + noun of place or time
Please go back to the beginning of your story.
The children went back to the museum to see the new exhibit.

Verbs often used before back to:
crawl, drive, fly, go, hark, jump, look, move, race, run, think, walk

Pattern 2: verb + noun + back to + noun
We took the train back to the city.

Typical verbs:
bring, carry, drive, push, pull, take

2. Back from indicates return to a starting place from a different place.

Pattern: verb + back from + noun of place
I'll be back (home) from the store in about ten minutes.
We can't leave until your mother gets back from her trip.

Typical verbs before back from:
be, come, drive, fly, get, move, run, walk

3. Back indicates a return of something.

Pattern 1: verb + noun + back (+ to + noun)
Please give this plate back to your mother.
I took the dress back to the store because it didn't fit.

Typical verbs:
bring, give, pay, send, take

Pattern 2: verb + noun + back (+ from + noun)
Please get my suit back from the cleaners.

Pattern 3: verb + noun + back (adverb) I called you back when I got home.

Typical verbs:
call, bring, pay, put, take

4. Phrasal verbs

get back (intransitive)—move out of the way
We wanted to see the action, but they made us get back.

get back to someone (nonseparable)—call someone with new information
As soon as I know the figures, I will get back to you.

get back at someone (nonseparable)—do harm in return for a wrong
After he was fired, he tried to get back at his boss.

Electricity

Generating electricity

Electricity is mostly generated in places called power stations. Most power stations use heat to boil water into steam which turns a steam engine. The steam engines turbine turns a machine called a generator. Generators have wires inside which spin inside a magnetic field. Electromagnetic induction causes electricity to flow through the wires.

There are many sources of heat which can be used to generate electricity. Heat sources can be classified into two types renewable energy resources in which the supply of heat energy never runs out and non renewable energy resources in which the supply will be eventually used up. Sometimes a natural flow, such as wind power or water power, can be used directly to turn a generator so no heat is needed.