558
12 Electric Circuits
12.14 R =
V 2
P
=
(100) 2
60
= 166.7
R = R 0 (1 + αt)
t =
R − R 0
R 0 α
=
166.7 − 20
20 × 0.0052
= 1410
◦ C.
12.15 Let a current of 6 A be sent through the corner a. Let a potential difference
V ab be established between a and b and current 6 A flow out from b. The
currents in various branches are indicated in Fig. 12.37 from symmetry considerations. If R eq is the equivalent resistance of this network across the body
diagonal ab
V ab = 6 R eq
But V ab = V ac + V cd + V db
= 2R + R + 2R = 5R
∴ 6 R eq = 5R
or R eq =
5
6
R =
5
6
× 10 = 8.33
Fig. 12.37
12.16 W = V 2 /R
R 1 =
V 2
W 1
=
(220) 2
25
= 1936
R 2 =
V 2
W 2
=
(220) 2
100
= 484
12 Electric Circuits
12.14 R =
V 2
P
=
(100) 2
60
= 166.7
R = R 0 (1 + αt)
t =
R − R 0
R 0 α
=
166.7 − 20
20 × 0.0052
= 1410
◦ C.
12.15 Let a current of 6 A be sent through the corner a. Let a potential difference
V ab be established between a and b and current 6 A flow out from b. The
currents in various branches are indicated in Fig. 12.37 from symmetry considerations. If R eq is the equivalent resistance of this network across the body
diagonal ab
V ab = 6 R eq
But V ab = V ac + V cd + V db
= 2R + R + 2R = 5R
∴ 6 R eq = 5R
or R eq =
5
6
R =
5
6
× 10 = 8.33
Fig. 12.37
12.16 W = V 2 /R
R 1 =
V 2
W 1
=
(220) 2
25
= 1936
R 2 =
V 2
W 2
=
(220) 2
100
= 484