Question

36.
Analyse the given circuit and answer the following questions;
R1=5
R2= 10
R3= 9
R4=7
V=10
(i) Find out the total resistance of the circuit.
(i) What is the amount of current flowing through 7 Ohm resistor?
(iii) State any two reasons for alloys being used to make heating element.
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Answer 1

$\tt \: i)total \: resistance \: \\ \tt \: R_1 + \frac{1}{R_2} + \frac{1}{R_3} + R_4 \\ \\ \tt \: 5 + \frac{1}{10} + \frac{1}{9} + 7 \\ \\ \tt \: 5 + \frac{9 + 10}{90} + 7 \\ \\ \tt \: 5 + \frac{19}{90} + 7 \\ \\ \tt \: \frac{450}{90} + \frac{19}{90} + 7\\ \\ \tt \: \frac{450 + 19}{90} + 7\\ \\ \tt \: \frac{469}{90} + \frac{630}{90} \\ \\ \tt \: \frac{469 + 630}{90} \\ \\ \tt \: \frac{1099}{90} \\ \\ \tt \:12.21 \: ohm \\ \\ \tt \: ii)as \: we \: know \: that\\ \\ \tt \:v = ir \\ \tt \: or \: \: \: \: { \red{i = \frac{v}{r} }} \\ \\ \tt \:so \: i = \frac{10}{7} = 1.42\: amp.$

iii)

• Alloys have High melting points and resistivity.
• Alloys don't readily oxididse.

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