Given a scientific passage and an answer, generate a question for the given answer.

Passage: Any magnet has two ends called poles where the magnetic effect is strongest. Answer: poles
What do you call the two ends of a magnet where the magnetic effect is strongest?

Passage: If the experimental value is less than the accepted value, the error is negative. If the experimental value is larger than the accepted value, the error is positive. Often, error is reported as the absolute value of the difference in order to avoid the confusion of a negative error. The percent error is the absolute value of the error divided by the accepted value and multiplied by 100%. Answer: negative
If the experimental value is less than the accepted value, the error is what?

Passage: Thermal energy is converted to the kinetic energy of the moving piston inside the cylinder. The moving piston, in turn, can be used to turn a turbine or do other useful work. Answer: kinetic energy
Inside a cylinder, thermal energy is converted to what type of energy of the moving piston?