Question

Лампочка и реостат соединены последовательно и подключены к источнику тока. Напряжение на зажимах лампочки 40В, сопротивление реостата 60 Ом. Внешняя цепь потребляет мощность 120 Вт. Найти силу тока в цепи.

Answer 1

I=U/R; N=U*I; I=N/U;I=120/40=3(А)

Answer 2

Calculation of Current in the Circuit

To find the current in the circuit, we can use Ohm's Law, which states that the current flowing through a conductor is equal to the voltage across the conductor divided by its resistance.

In this case, the voltage across the lamp is given as 40V, and the resistance of the rheostat is given as 60Ω. The external circuit consumes a power of 120W.

Using the formula P = IV, where P is power, I is current, and V is voltage, we can calculate the current in the circuit.

Let's calculate the current step by step:

1. Calculate the resistance of the lamp: The resistance of the lamp can be calculated using Ohm's Law: R = V/I, where R is resistance, V is voltage, and I is current. Rearranging the formula, we get I = V/R. Given that the voltage across the lamp is 40V, we can calculate the resistance of the lamp as follows: R_lamp = V_lamp / I_lamp = 40V / I_lamp

2. Calculate the power consumed by the lamp: The power consumed by the lamp can be calculated using the formula P = IV, where P is power, I is current, and V is voltage. Rearranging the formula, we get I = P/V. Given that the power consumed by the external circuit is 120W, we can calculate the current flowing through the lamp as follows: I_lamp = P_external / V_lamp = 120W / 40V

3. Calculate the total resistance in the circuit: The total resistance in the circuit is the sum of the resistance of the lamp and the resistance of the rheostat. R_total = R_lamp + R_rheostat

4. Calculate the current in the circuit: Using Ohm's Law, we can calculate the current in the circuit as follows: I_total = V_total / R_total

Let's calculate the current in the circuit using the given values:

1. Calculate the resistance of the lamp: R_lamp = 40V / I_lamp

2. Calculate the power consumed by the lamp: I_lamp = 120W / 40V

3. Calculate the total resistance in the circuit: R_total = R_lamp + 60Ω

4. Calculate the current in the circuit: I_total = 40V / R_total

Now, let's substitute the given values and calculate the current in the circuit.

1. Calculate the resistance of the lamp: R_lamp = 40V / I_lamp = 40V / (120W / 40V) = 40V / 3A = 13.33Ω

2. Calculate the power consumed by the lamp: I_lamp = 120W / 40V = 3A

3. Calculate the total resistance in the circuit: R_total = R_lamp + 60Ω = 13.33Ω + 60Ω = 73.33Ω

4. Calculate the current in the circuit: I_total = 40V / R_total = 40V / 73.33Ω ≈ 0.545A

Therefore, the current in the circuit is approximately 0.545A.

Please note that the calculations provided are based on the given information and assumptions.