Energy in systems (thermal, chemical, electrical) Knowledge-Based Practice

Questions

1. 1.

   In a direct-current circuit consisting of a chemical cell connected to a resistor, what is the primary role of the cell in terms of energy in the system?

   • A) It generates new electric charge carriers and pumps them into the circuit while absorbing thermal energy.
   • B) It uses stored chemical energy to raise the electrical potential energy of charge carriers moving through it.
   • C) It converts thermal energy from the environment directly into the kinetic energy of conduction electrons.
   • D) It stores electrostatic charge passively without altering its internal chemical energy stores during operation.
2. 2.

   When an electric current flows through a metallic conductor, which microscopic process is directly responsible for converting electrical energy into thermal energy?

   • A) The continuous breakdown and reformation of metallic chemical bonds between adjacent atoms
   • B) The spontaneous emission of high-energy photons during electron transitions between core shells
   • C) The direct absorption of electric field lines by the atomic nuclei of the metal
   • D) Collisions between accelerated conduction electrons and the vibrating lattice ions of the metal
3. 3.

   A closed system receives energy via an electric current at a constant rate while simultaneously transferring thermal energy to its surroundings at the exact same rate. What is the net change in the internal energy of the system over this time interval?

   • A) The internal energy increases continuously because electrical energy input always exceeds thermal energy transfer.
   • B) The internal energy decreases steadily because thermal energy transferred out of a system cannot be fully replenished.
   • C) The internal energy drops to zero because electrical energy and thermal energy cancel each other out completely.
   • D) The internal energy remains constant because the rate of energy entering the system equals the rate of energy leaving the system.
4. 4.

   An electric current flows through a resistive heating element enclosed inside a perfectly insulated container of liquid. Assuming no energy is transferred to the external surroundings, which statement correctly describes the energy changes in the system?

   • A) The electrical energy delivered is stored entirely as chemical potential energy within the bonds of the liquid.
   • B) The increase in thermal energy is greater than the electrical energy delivered because electrical charge accumulates inside the resistor.
   • C) A portion of the electrical energy is permanently destroyed because electrical resistance opposes current flow.
   • D) The increase in the internal thermal energy of the system is exactly equal to the total electrical energy delivered.
5. 5.

   During the complete combustion of a hydrocarbon fuel inside a domestic heating furnace, which primary energy transformation takes place?

   • A) Thermal energy is transformed into chemical energy.
   • B) Electrical energy is transformed into thermal energy.
   • C) Chemical energy is transformed into electrical energy.
   • D) Chemical energy is transformed into thermal energy.
6. 6.

   During a sustained endothermic process, such as the thermal decomposition of calcium carbonate in a high-temperature kiln, which primary energy transformation takes place?

   • A) Thermal energy is converted into chemical potential energy.
   • B) Chemical potential energy is converted into thermal energy.
   • C) Thermal energy is converted into electrical energy.
   • D) Electrical energy is converted into chemical potential energy.
7. 7.

   Which primary energy transformation takes place inside a thermoelectric generator when it produces an electric current across a temperature gradient?

   • A) Electrical energy into thermal energy
   • B) Thermal energy into electrical energy
   • C) Chemical energy into electrical energy
   • D) Mechanical energy into electrical energy
8. 8.

   During the recharging of an accumulator (secondary cell) using an external power source, which energy transformation primarily occurs inside the cell?

   • A) Chemical energy is transformed into electrical energy.
   • B) Electrical energy is transformed into chemical energy.
   • C) Thermal energy is transformed into electrical energy.
   • D) Electrical energy is transformed into thermal energy.
9. 9.

   A hydrogen-oxygen fuel cell operates continuously to supply power to an external electrical circuit. Which statement correctly describes the primary energy transformation that occurs inside the fuel cell?

   • A) Electrical energy is converted into chemical energy stored within the newly formed water molecules.
   • B) Chemical energy stored in the reactant molecules is converted directly into electrical energy.
   • C) Thermal energy from combustion is converted into mechanical work and then into electrical energy.
   • D) Thermal energy absorbed from the surroundings is converted directly into chemical potential energy.
10. 10.

    A portable immersion heater powered by a chemical battery is used to heat a beaker of water. Which sequence correctly describes the primary energy transformations occurring in this system?

    • A) Thermal energy → electrical energy → chemical energy
    • B) Chemical energy → electrical energy → thermal energy
    • C) Electrical energy → chemical energy → thermal energy
    • D) Chemical energy → thermal energy → electrical energy

Answers and step-by-step solutions appear after you finish the test.