Resistance of a wire is directly proportional to its length and inversely proportional to the square of its radius.
Thus, if the length is doubled, and the radius is halved:
R₂ = 2R₁/(1/2)²
R₂ = 8R₁
Therefore the resistance increases eight times.
Answer:
Explanation:
Magnetic field due to a long current carrying conductor
μ₀ / 4π x 2i / r ( i = current , r = distance of point from wire )
= 10⁻⁷ x 2 x 120 / 6.4 ( i = 120 A , r = 6.4m )
= 37.5 x 10⁻⁷ T .
= 3. 75 X 10⁻⁶ T .
= 3.75 µT.
b )
The direction of this field will be horizontal hence it will affect magnetic needle.
Answer: D. When both objects reach the same temperature.
Explanation: When will heat flow between the objects stop? Heat will always flow from the warmer object to the colder object. The heat transfer will stop when the two objects are at the same temperature and reach thermal equilibrium.
