Find new resistance of wire if it is stretched to twice its original length. Original resistance was 20 ohm. Also how its
resistivity will change

Original Length = L1

Stretched length =L2

From

R = pl/A

R=Resistance

p=Resistivity

A=Cross-sectional Area

l= length of wire

We can see that Resistance is directly Proportional to Length... Meaning that Resistance Increases also as Length increases.

R1/L1 = R2/L2

From the question... The key to note is this sentence

"The Stretched length is TWICE the Original Length"

Meaning

L2 = 2L1 (So replace L2 as 2L1 when solving)

R1=20ohms

Let R2 = k

Applying the formula

20/L1 = k/2L1

kL1 = 20x 2 L1

KL1 = 40L1

L1 cancels on both sides

k=40ohms.

So As the length doubled... The Resistance did too

from 20ohms to 40ohms

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.