Question

The power supplied by a machine will always be _________ the power supplied to the machine in real conditions?

1) greater than
2) equal to
3) less than
4) cannot be determined

Answer 1

The power supplied by a machine is less than the power supplied to the machine in real conditions due to the relationship between power, voltage, and resistance.

Step-by-step explanation:

The power supplied by a machine will always be less than the power supplied to the machine in real conditions.

According to the expression for electric power, P = V²/R, the power delivered is inversely proportional to the resistance connected to the voltage source. Therefore, the lower the resistance, the greater the power delivered. Additionally, since voltage is squared in the formula, applying a higher voltage can have a larger effect on the power.

For example, if the voltage is doubled to a 25-W bulb, its power nearly quadruples to about 100 W. However, if the bulb's resistance remained constant, its power would be exactly 100 W. With a higher temperature, the bulb's resistance increases, leading to a lower power output.

Answer 2

In real conditions, the power delivered by a machine is less than the power supplied due to inefficiencies such as heat loss and resistance, even though transformer efficiency can be very high.

Therefore, the correct answer to the student's question is 3) less than.

Step-by-step explanation:

The power supplied by a machine will always be less than the power supplied to the machine in real conditions. This is due to real-world inefficiencies such as friction, heat loss, and resistance. In the context of electrical systems, for instance, the power dissipated in a resistor due to its resistance results in less power being delivered than is supplied. When considering transformers, it is nearly true in practice that the electrical power output of a transformer equals its input, assuming resistance is negligible. However, transformer efficiency, while often exceeding 99%, does not equate to 100%, meaning some power is still lost. Therefore, the correct answer to the student's question is 3) less than.