Question

Two long parallel wires are hung by 4 cm long cords from a common axis. The wires have mass 0.0125 kg/m and carry equal currents in opposite direction. Find the current in each wire if the cords hang at 6⁰ with the vertical as shown in Fig. (1) –

• A. 11.2 A
• B. 22.3 A
• C. 717 A
• D. 71.7 A

Answer 1

Answer: (B)

22.3 A

Answer 2

$\frac { \mathrm { dF } } { \mathrm { dl } }$rep == T sin 6^b$\frac { \mathrm { mg } } { 4 }$= T cos 6⁰

tan 6⁰ =$\frac { \mu _ { 0 } \mathrm { I } ^ { 2 } } { 4 \pi \mathrm { dmg } }$=$\sqrt { \frac { \tan 6 ^ { \circ } \left( 4 \pi 4 \sin 6 ^ { \circ } \right) \mathrm { mg } \times 10 ^ { - 2 } } { \mu _ { 0 } } }$

=$\sqrt { \frac { ( .1 ) ^ { 2 } \times 4 \pi \times 4 \times .0 .125 \times 10 \times 10 ^ { - 2 } } { 4 \pi \times 10 ^ { - 7 } } }$= 22.3 A

Fig. (2) Fig. (3)

tan 6⁰ = sin 6⁰ =$\frac { 6 \times \pi } { 180 }$= .1