Energy and Power

Free sample questions

Energy and Power — sample Science questions with answers

1. Question 1

   What is the S.I. unit of energy?

   • AWatt
   • BJoule
   • CNewton
   • DKilogram

   Answer: B. Joule

   Energy is measured in joules (J). Watt is the unit of power, Newton the unit of force, kilogram the unit of mass.

2. Question 2

   An object with mass $2\text{kg}$ falls from a height of $5\text{m}$. What is the gravitational potential energy of the object? (Assume $g=10{\text{m/s}}^2$)

   • A$10\text{J}$
   • B$20\text{J}$
   • C$50\text{J}$
   • D$100\text{J}$

   Answer: D. $100\, \text{J}$

   Gravitational potential energy = mass × gravitational acceleration × height = $2\times 10\times 5=100\text{J}$.

3. Question 3

   Which of the following is NOT a form of energy?

   • AThermal energy
   • BKinetic energy
   • CGravitational energy
   • DChemical energy

   Answer: C. Gravitational energy

   "Gravitational energy" is not the correct term; the form of energy related to gravity is gravitational potential energy. The other options are valid forms of energy.

4. Question 4

   What is meant by power?

   • ARate of energy consumption
   • BTotal amount of energy used
   • CForce applied
   • DDistance travelled

   Answer: A. Rate of energy consumption

   Power is the rate of doing work or the rate of energy transfer, i.e., energy per unit time.

5. Question 5

   A bulb uses energy of $600\text{J}$ in $10\text{s}$. What is the power of the bulb?

   • A$6\text{W}$
   • B$60\text{W}$
   • C$600\text{W}$
   • D$6000\text{W}$

   Answer: B. $60\, \text{W}$

   Power = energy / time = $600\text{J}/10\text{s}=60\text{W}$.