Answer:

Explanation:
Velocity of wave in stretched string is given by the formula

here we know that
T = 4 N
also we know that linear mass density is given as

so we have

now the tension in the string is double
so the velocity is given as


<h3><u>Answer;</u></h3>
1st drop; Motor
2nd drop; Electricity
A device that uses electricity and magnetism to create motion is called a <u>motor</u>. In a reverse process, a device that uses motion and magnesium can be used to create <u>electricity</u>.
<h3><u>Explanation</u>;</h3>
- <em><u>Motors are device which use electricity and magnetism to create motion.</u></em> They pass alternating current through opposing pairs of magnets to create a rotating magnetic field which creates a magnetic field in the rotor of a motor, making it to spin around.
- <em><u>Electric motors work in a reverse process by using motion and magnetism to generate electricity. </u></em>When a coil or loops of wire are exposed to a changing magnetic field, an electrical current arises or is induced.
The circuit change when a wire is added is, an open circuit occurs and makes all bulbs turn off.
<h3>What is a closed circuit?</h3>
A closed circuit is a type of circuit connection in which the wire connection is complete and current flow occurs, turning the light bulbs on in the process.
<h3>What is an open circuit?</h3>
An open circuit is a type of circuit connection in which the wire connection is incomplete and current cannot flow, turning off the light bulbs.
Thus, the circuit change when the wire is added is, an open circuit occurs and makes all bulbs turn off.
Learn more about open circuit here: brainly.com/question/20351910
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Using coils of fewer turns on the electromagnet
It is typically 30 km to 50 km thick.