Physics Exam Revision

The 1st law of Thermodynamics:

• Energy can not be created or destroyed. It just changes forms.

• Energy can only be created by the sun

• Some energy is lost to the environment.

What does the "U" stand for the formula ∆U = Q – W

• Heat

• Temperature

• Work

• Internal energy

The transfer of thermal energy between objects of different temperatures is called ________

• Temperature

• Heat

• internal energy

• none of these

If Q = + 20 J, W = - 30 J, so the change in thermal energy of the system =

• - 50 J

• 50 J

• -10 J

• 20 J

A heat engine:

• converts heat input to an equivalent amount of work

• converts work to an equivalent amount of heat

• takes heat in, does work, and loses energy heat

• uses positive work done on the system to transfer heat

• from a low temperature reservoir to a high temperature

What is the order of operation of a 4 stroke engine

• Intake, Power, Compression, Exhaust

• Exhaust, Intake, Compression, Power

• Intake, Compression, Power, Exhaust

• Compression, Exhaust, Power, Intake

When the work done by the system = the heat supplied to the

system, the efficiency is equal to

• 0

• 1

• 0.5

• 0.1

A refrigerator is:

• Heat engine

• An electric motor

• Heat engine working in backward direction

• Air cooler

a device that uses electric energy to pump thermal energy from a cooler location to a warmer location.

• heating appliance

• thermostat

• refrigerator

• heat engine

a machine that converts thermal energy into mechanical energy

• heating appliance

• thermostat

• refrigerator

• heat engine