The properties of magnets are used to make electricity. Moving magnetic fields pull and push electrons. ... Moving a magnet around a coil of wire, or moving a coil of wire around a magnet, pushes the electrons in the wire and creates an electrical current.

4 0

1 year ago

A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then the plates are pulled apart to twic

Igoryamba

Answer: C.

Explanation:

For a parallel-plate capacitor where the distance between the plates is d.

The capacitance is:

C = e*A/d

You can see that the distance is in the denominator, then if we double the distance, the capacitance halves.

Now, the stored energy can be written as:

E = (1/2)*Q^2/C

Now you can see that in this case, the capacitance is in the denominator, then we can rewrite this as:

E = (1/2)*Q^2*d/(e*A)

e is a constant, A is the area of the plates, that is also constant, and Q is the charge, that can not change because the capacitor is disconnected.

Then we can define:

K = (1/2)*Q^2/(e*A)

And now we can write the energy as:

E = K*d

Then the energy is proportional to the distance between the plates, this means that if we double the distance, we also double the energy.

8 0

2 years ago

Per person, the energy consumption in the United States is about 3.3 × 10^8 Btu/yr. This is equivalent to a power of:________. A

zhuklara [117]

Answer:

$3.3\times 10^8\ btu/yr=11\ kW$

Explanation:

Btu of British thermal unit is a unit of heat. The relation between btu/year and watts is given by :

$1\ btu/yr=3.343\times 10^{-5}\ W\\\\3.3\times 10^8\ btu/yr=3.343\times 10^{-5}\times 3.3\times 10^8\ W\\\\3.3\times 10^8\ btu/yr=11031.9\ W\\\\3.3\times 10^8\ btu/yr=11\ kW$

So, $3.3\times 10^8\ btu/yr$ is equal to 11 kW. Hence, the correct option is (d).

4 0

2 years ago