Physics Fundamentals: Work, Heat Transfer, and Electrical Circuit Calculations

Posted on Nov 1, 2025 in Physics

Work, Power, and Energy Calculations

• Work Done Lifting a Load

  Question: How much work is done in lifting a 500 kg load to a height of 40 m?

  Answer: 1.96 × 10⁸ J

• Motor Power Calculation

  Question: How powerful is a motor that can lift a 1200 kg load 10 m in 20 s?

  Answer: 5886 Watts

• Work and Lifting Height

  Question: Which of the following statements is true regarding the work associated with lifting a box to a certain height?

  Answer: All of these will require the same amount of work.

• Law of Conservation of Energy

  Question: Which of the following best describes the law of conservation of energy?

  Answer: The total energy going into a closed system must be equal to the total energy coming out of the closed system.

• Work Done Accelerating an Object

  Question: How much work is done in accelerating a 20 kg object from 2.00 m/s to 7.50 m/s?

  Answer: 523 J

Thermodynamics and Heat Transfer Concepts

Heat Transfer Mechanisms

• Kinetic Molecular Theory

  Question: Which of the following statements best describes the kinetic molecular theory?

  Answer: As an object heats up, the molecules within that object start to move more.

• Heat Transfer by Conduction

  Question: Which of the following statements best describes heat transfer by conduction?

  Answer: The transfer of heat between materials through direct contact of molecules.

• Heat Transfer by Convection

  Question: Which of the following statements best describes heat transfer by convection?

  Answer: The transfer of heat between materials through a fluid that is in motion.

• Heat Transfer by Radiation

  Question: Which of the following statements best describes heat transfer by radiation?

  Answer: The transfer of heat through electromagnetic waves or light.

Thermal Energy Calculations

• Change in Thermal Energy (Ice)

  Question: What is the change in thermal energy if the ice is heated from 50 K to 250 K?

  Answer: 420 J

• Change in Temperature (Cooling)

  Question: What is the change in temperature if the ice is cooled such that ΔE = -350 J?

  Answer: -166 K

• Specific Heat Capacity Determination

  Question: Determine the specific heat capacity of the ice by using the graph.

  Answer: 2.1 J/g · K

• Kiln Efficiency Calculation

  Question: A 715 kW kiln is able to heat 400 kg of lead from 270 K to 600 K. How efficient is the kiln?

  Answer: 10%

• Energy Conversion (kWh to Joules)

  Question: The electrical meter outside your house reads 3.15 kWh. How much energy is this in Joules?

  Answer: 1.13 × 10⁷ J

Fundamentals of Electricity and Circuit Analysis

Electrical Concepts

• Conventional Current Direction

  Question: In what direction does conventional current go?

  Answer: In the direction of positive-charge flow.

• Conductor Definition

  Question: Concerning electricity, a conductor is best described as:

  Answer: A material that doesn’t allow electric charges to pass through it.

  (Note: This definition typically describes an insulator, but the text is preserved as provided.)

• Methods to Charge an Object

  Question: Which of the following is not a method to charge an object?

  Answer: Ionization

• Definition of Current

  Question: Which of the following best describes current?

  Answer: Current is the change in charge over some time in a wire.

• Definition of Resistance

  Question: Which of the following best describes resistance?

  Answer: An object in a circuit that causes voltage loss.

Circuit Calculations and Analysis

• Electron Flow Calculation

  Question: How many electrons pass through a wire in 20 min, if that wire carries a current of 30 A, if each electron has a charge of 1.602 × 10^-19 C?

  Answer: 2.25 × 10²³ e^–

• Terminal Voltage Determination

  Question: If the EMF is 3.70 V, with an internal resistance of r = 0.025 Ω. Determine the voltage of the terminal.

  Answer: 3.67 V

• Effect of Doubling Resistance

  Question: The internal resistance, r, and the resistor, R, are suddenly doubled.

  Answer: It doesn’t change.

• Effect of Halving EMF

  Question: The EMF is cut in half, while the internal resistance and the resistor are unchanged (from question 8).

  Answer: It gets cut in half.

• Equivalent Resistance (Conceptual)

  Question: Determine the equivalent resistance of the circuit.

  Answer: 2R

• Current in Simplified Circuit

  Question: If the voltage of the terminal is 18 V, and each resistor has a resistance of 4 Ω, what is the current of the simplified circuit?

  Answer: 2.25 A

• Current in Parallel Resistors

  Question: What is the current that passes through one of the parallel resistors?

  Answer: 1.125 A

• Equivalent Resistance (Numerical)

  Question: Determine the equivalent resistance of the circuit.

  Answer: 1.83 Ω

• Current from the Terminal

  Question: Determine the current that comes from the terminal.

  Answer: 27.3 A

• Current Through Specific Resistor

  Question: Determine the current that passes through the 5.2 Ω resistor.

  Answer: 9.62 A

• Voltage Loss Across Resistors

  Question: What can be said about the voltage loss across each resistor?

  Answer: They are all equal. (Implies a parallel configuration.)

• Current Through Resistor R

  Question: Determine the current that passes through R.

  Answer: 4 A

• Determining Resistor Values

  Question: If the supply voltage is 120 V, determine the values of R2 and R3.

  Answer: R2 = 7.5 Ω (R3 value is not provided.)