(Problems)
Introductory Concept of Electrical Circuits
Electric Current
1. A hair dryer draws a current of 3A. If it is switched
on for 5 minutes,
a. How much charge, and
b. How many electrons have passed through it?
Given:
𝑄= ?
𝑡 = 5𝑚𝑖𝑛 × 60 = 300𝑠𝑒𝑐
𝐼 = 3𝐴
Solution:
a. 𝑄 = 𝐼 × 𝑡
𝑄 = 3𝐴 × 300𝑠𝑒𝑐
𝑄 = 900𝐶 ANS
−19
b. Charge of 1 electron = 1. 6 × 10 𝐶
900𝐶
No. of electrons = −19
1.6×10 𝐶
21
No. of electrons = 5. 625 × 10 ANS
, Electrical Properties of Materials
Resisitivity
1. A wire 12m long has a resistance of 1. 5Ω. What will
be the resistance of 16m of the same wire?
Given:
𝐿1 = 12𝑚
𝑅1 = 1. 5Ω
𝐿1 = 16𝑚
𝑅1 = ?
Solution:
𝑅1
𝑅1 = 𝐿1
𝐿2
1.5Ω
𝑅1 = 12𝑚
16𝑚
24Ω𝑚
𝑅1 = 12𝑚
𝑅1 = 2Ω ANS