Question

A voltmeter is used to determine the voltage across a parallel plate capacitor; the positive plate has a 400 kV higher electric potential than the negative plate.
1) In eV, how much will the potential energy of a proton change by moving it from near the negative plate to near the posivite plate?

2) In eV, how much will the potential energy of an electron change by moving it from near the negative plate to near the positive plate?

Answer 1

Answer:

Part a)

$\Delta U = 4\times 10^5eV$

Part b)

$\Delta U = -4\times 10^5eV$

Explanation:

Part a)

Change in potential energy of a charge is given as

$\Delta U = q\Delta V$

here we know that

$q = e$ for proton

also we have

$\Delta V = 400 kV$

now we have

$\Delta U = e(400 kV)$

$\Delta U = 4\times 10^5eV$

Part b)

Change in potential energy of a charge is given as

$\Delta U = q\Delta V$

here we know that

$q = -e$ for proton

also we have

$\Delta V = 400 kV$

now we have

$\Delta U = -e(400 kV)$

$\Delta U = -4\times 10^5eV$