Uma espira circular condutora de raio 30 cm é percorrida por uma corrente elétrica de intensidade 2,0 A, no sentido anti-horário. Outra espira de raio 15 cm é concêntrica à anterior e está situada no mesmo plano da primeira. Determine a intensidade e o sentido da corrente elétrica que, percorrendo a segunda espira, anula o vetor indução magnética resultante no centro do sistema. (Considere: µ0 = 4π.10-7 T. m/A e π = 3,0).

Acylinder with a movable piston contains 11.7 moles of a monatomic ideal gas at a pressure of 1.32×10^5 pa. the gas is initially at a temperature of 300 k. an electric heater adds 43200 j of energy into the gas while the piston moves in such a way that the pressure remains constant. cp=20.79 j k^−1 mol^−1 for a monatomic ideal gas, and that the number of gas molecules is equal to avogadro's number (6.022×10^23) times the number of moles of the gas. (a) what is the temperature of the gas after the energy is added? (b) what is the change in volume of the gas? (c) how much work is done by the gas during this process?

Aria drove to the store, did some shopping, and then came home. during maria's trip, when was her displacement equal to zero?

Does heating a metal wire increase or decrease its electrical resistance? why?