Answer:
The ratio of the diameter of iron to Cu is;

Explanation:
R=(ρL)/A
- R is resistance,
- L is length,
- A is area,
- ρ is resistivity
- d is diameter
from the question the two materials have the same resistance per unit length.

for iron =
for copper
This means we can equate ρ/A for both materials.

re-arranging the equation we have,





The formula for the energy in a capacitor , u in terms of q and c is q²/2c
<h3>What is the energy of a capacitor?</h3>
The energy of a capacitor u = 1/2qv where
- q = charge on capacitor and
- v = voltage across capacitor.
<h3>What is the capacitance of a capacitor?</h3>
Also, the capacitance of a capacitor c = q/v where
- q = charge on capacitor and
- v = voltage across capacitor.
So, v = q/c
<h3>
The formula for energy of the capacitor in terms of q and c</h3>
Substituting v into u, we have
u = 1/2qv
= 1/2q(q/c)
= q²/2c
So, the formula for the energy in a capacitor , u in terms of q and c is q²/2c
Learn more about energy in a capacitor here:
brainly.com/question/10705986
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hola ya sabes la respuesta si si ,me la dices porfa
Answer: That's air resistance.
Explanation: Well, air resistance is an upward force exerted on falling objects.
( I hope this helped <3 )