Solution of Problems from several topics like- Electric Potential Energy; Current, Resistance & Power; Capacitance; RC Circuit

1. PRACTICE PROBLEMS
FOR
FINAL EXAM

2. ESSENTIAL FORMULAS

3. ESSENTIAL FORMULAS

4. ESSENTIAL FORMULAS

5. ESSENTIAL FORMULAS
Necessary
Formulas

6. ESSENTIAL FORMULAS

7. ESSENTIAL FORMULAS

8. ESSENTIAL FORMULAS
Necessary
Formulas
Doubl
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10. 1. An electron is accelerated from rest through a potential difference 12 V. What is
the change in electric potential energy of the electron ?
Answer in Next
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12. 3. What distance must separate two charges of + 5.6×10-4C and -6.3×10-4 C in
order to have an electric potential energy with a magnitude of 5.0 J in the
system of the two charges?

13. Question>> What is the electric potential at point P, located at the center of
the square of point charges shown in Fig. 1a? The distance d is 1.3 m, and
the charges are q1=+12 nC, q2=-24 nC, q3=+31 nC and q4=+17 nC, which
are held at the corners of a square as shown in Fig. 1a. (a) Calculate the net
electric potential at point P, at the center of the square.
Answer in Next Page>>

15. • A rectangular block of iron has dimensions 1.2 cm & 1.2 cm & 15 cm. A potential
difference is to be applied to the block between parallel sides and in such a way that
those sides are equipotential surfaces (as in Fig. 2). What is the resistance of the block
if the two parallel sides are (1) the square ends (with dimensions 1.2 cm & 1.2 cm) and
(2) two rectangular sides (with dimensions 1.2 cm & 15 cm)?
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Figure 2

17. Answer in Next
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19. • A bulb is rated as 25-Watt -250 Volt. On connecting this bulb to a mains of
250 volts, what will be the value of current (I) flowing in it, and how much
resistance (R) will the bulb provide to this flow of current?

20. Question>> A heating element is made by maintaining a potential difference of 75.0
V across the length of a Nichrome wire that has a 2.60 x 10-6 m2 cross section.
Nichrome has a resistivity of 5.00 x 10-7 Ω m. (a) If the element dissipates 5000W, what is its
length? (b) If a potential difference of 100 V is used to obtain the same dissipation
what should the length be?

21. 3. Two resistors are wired in series. The second resistor has twice the resistance
as the first. Current passes through the combination. Compared to the current
let us say 3 amp flowing through the first resistor, what would be the current
through the second resistor?

22. 4. What will happen to the brightness of the bulb in the side Fig. 4, if the
resistance of R2 is increased and R1 remains constant? The resistance of the
bulb is Rbulb.
Answer :
The relationship between brightness and
resistance of bulbs connected in a series is
directly proportional. Therefore, the bulb with the higher resistance will shine
brighter. Therefore, the bulb with the lower resistance will shine brighter. In
parallel, both bulbs have the same voltage across them. The bulb with the lower
resistance will conduct more current and therefore have a higher power
dissipation and brightness.