We use the formula V=IR where I is current, v is voltage, and R is resistance. This is V=(3)(10) which is 30 Volts, answer choice (c)
You need to attach the answer choices
Hello there!
Essentially, a control variable is what is kept the same throughout the experiment, and it is not of primary concern in the experimental outcome. Any change in a control variable in an experiment would invalidate the correlation of dependent variables (DV) to the independent variable (IV), thus skewing the results.
The answer is: 120V
Power is the rate at which energy is supplied/transformed in time:
we can write:
V ddp in Volts represents Energy/Charge i.e. energy carried by each coulomb;
I current in Amperes represents Charge/time or coulombs passing each seconds.
combining them we have:
Power = energy/time = V • 1
or
1200 = V ⋅ 10
V = 1200/10 = 120V
The text does not specify whether the resistance R of the wire must be kept the same or not: here I assume R must be kept the same.
The relationship between the resistance and the resistivity of a wire is

where

is the resistivity
A is the cross-sectional area
R is the resistance
L is the wire length
the cross-sectional area is given by

where r is the radius of the wire. Substituting in the previous equation ,we find

For the new wire, the length L is kept the same (L'=L) while the radius is doubled (r'=2r), so the new resistivity is

Therefore, the new resistivity must be 4 times the original one.