When the sliding rheostat R is adjusted and the motor is stopped, the indication of ammeter and voltmeter are 0.50a and 2.0V respectively. When R is re adjusted and the motor returns to normal operation, the indication of ammeter and voltmeter are 2.0A and 24.0V respectively. Then the output power and internal resistance of the motor are normal They are () A. 32W and 4 Ω B. 48W and 4 Ω C. 32W and 12 Ω D. 48W and 12 Ω

When the sliding rheostat R is adjusted and the motor is stopped, the indication of ammeter and voltmeter are 0.50a and 2.0V respectively. When R is re adjusted and the motor returns to normal operation, the indication of ammeter and voltmeter are 2.0A and 24.0V respectively. Then the output power and internal resistance of the motor are normal They are () A. 32W and 4 Ω B. 48W and 4 Ω C. 32W and 12 Ω D. 48W and 12 Ω

Resistance of motor: r = UI = 20.5 Ω = 4 Ω; total power of motor: P = u1i1 = 24 V × 2A = 48 W; thermal power of motor resistance: PR = i12r = (2a) 2 × 4 Ω = 16 W; output power of motor in normal operation: P output = p-pr = 48 W-16 w = 32 W. so a is correct and BCD is wrong. So a

The resistance of the resistance wire of an electric furnace and the coil of a motor are the same, both of which are R. if the current passing through them is the same (the motor runs normally), then ()
A. The motor consumes more power than the furnace
B. The voltage at both ends of electric furnace is less than that of motor
C. The voltage at both ends of electric furnace and motor is equal
Answer, reason

The motor is not a pure resistance circuit. The thermal power consumed by the motor and the electric furnace is equal, but the total power of the motor is more than that of the electric furnace. Because the total power of the motor includes thermal power and mechanical power, and the total power is the product of voltage and current, AB is correct

There is a rocket with mass m in the air. It gets recoil force by jet and makes the rocket stand still in the air. The velocity V of the ejected gas is far less than m. The average power of the rocket can be calculated
The answer is MGV / 2
A solution to the problem of momentum impulse

To be clear, you can't do it without momentum theorem
This problem is to investigate the application of momentum theorem and kinetic energy theorem

Joule Lenz law
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This law is called Joule Lenz's law, i.e. q = C · ri2t. Where C is a proportional constant, the value of which depends on the unit chosen for measurement