Transfer Of Thermal Energy - Convection
Online Quiz - Convection
- 1.
An electrical heater is immersed in water. What is the main means in which heat is transferred from the heater to the water?
- A.
Conduction
- B.
Convection
- C.
Conduction and convection
- D.
None of the above
Correct Answer
C. Conduction and convectionExplanation
Thermal energy is conducted into the water. Convection currents also help the transfer of thermal energy as the water nearer the heater is hotterRate this question:
-
- 2.
Convection can occur in ___________.
- A.
Liquids only
- B.
Liquids and gases
- C.
Vacuum
- D.
Gases and solids
Correct Answer
B. Liquids and gasesExplanation
The particles must be mobile so that convection currents can be formed. Only particles in liquids and gases are mobile.Rate this question:
-
- 3.
The air in a large paper bag is heated. The bag is then found to rise through the surrounding cold air. This is because ________________.
- A.
The air in the bag has become less dense
- B.
The mass of the paper bag has decreased
- C.
The chemical compositions of the air in the bag has changed
- D.
The mass of the air in the bag has increased
Correct Answer
A. The air in the bag has become less denseExplanation
The volume of the air increases. Since density is mass over volume, the air will become less dense and rise.Rate this question:
-
- 4.
In a hot water tank, the heating element should be placed at the bottom because _________________.
- A.
Conduction cannot take place when the heater is at the top of the tank
- B.
The heated water will rise and form a convection current
- C.
Radiant heat travels faster in the upward direction
- D.
The heater must be covered by water at all times
Correct Answer
B. The heated water will rise and form a convection currentExplanation
Convection currents need to be formed. The hot water, which is less dense, must rise and the cold water, which is more dense, will sink to take its place.Rate this question:
-
- 5.
Water in a beaker is heated at X. Which diagram best shows the convection currents?
- A.
A
- B.
B
- C.
C
- D.
D
Correct Answer
D. DExplanation
Diagram D best shows the convection currents. In this diagram, the water in the beaker is heated at the bottom, causing it to become less dense and rise to the top. As the hot water rises, it displaces the cooler water, which then moves towards the bottom to replace it. This creates a continuous flow of water, known as convection currents.Rate this question:
-
- 6.
The diagram shows a crystal being heated in a beaker of water. The crystal releases a dye which shows how the water circulates around the beaker. What is happeningto cause the water above the crystal to rise?
- A.
The water contracts and its density decreases.
- B.
The water contracts and its density increases.
- C.
The water expands and its density decreases.
- D.
The water expands and its density increases.
Correct Answer
C. The water expands and its density decreases.Explanation
The water expands in volume. Since density is mass over volume, the air will become less dense and rise.Rate this question:
-
- 7.
In the process of convection, energy is transferred __________.
- A.
Because of density differences in a liquid
- B.
Because of temperature differences in a solid
- C.
By the diffusion of molecules through a fluid
- D.
By the vibration of molecules about a mean position
Correct Answer
A. Because of density differences in a liquidExplanation
In the process of convection, energy is transferred because of density differences in a liquid. This is because when there are variations in density within a liquid, it causes the warmer and less dense regions to rise while the cooler and denser regions sink. This movement of the fluid transfers energy from the warmer regions to the cooler regions, resulting in the transfer of heat.Rate this question:
-
- 8.
Which of the following methods would not produce convection currents in a container filled with water at 30oC?
- A.
Lighting a candle beneath the container
- B.
Floating a piece of ice on the water
- C.
Placing a lighted bulb just above the water surface
- D.
Dropping a piece of hot metal into the water
Correct Answer
C. Placing a lighted bulb just above the water surfaceExplanation
The hotter fluid must have room to rise while the colder fluid have room to sink.Rate this question:
-
- 9.
In very cold weather, ice can form on the surface of puddles of water because the air temperature is below that of the water. If the ice layer is found to be thickening at its lower surface, then thermal energy must be mostly _________________.
- A.
Conducted away from the ice through the air
- B.
Convected away from the ice through the water
- C.
Conducted from the upper to the lower surface of the ice
- D.
Convected towards the ice through the air
Correct Answer
A. Conducted away from the ice through the airExplanation
Thermal energy must be lost from the water to the air for the water to solidify. Convection cannot occur since ice is a solid.Rate this question:
-
- 10.
Which statement about convection is correct?
- A.
Brownian motion is a form of convection.
- B.
Convection occurs only in gases.
- C.
Convection results from a density change.
- D.
Evaporation is a form of convection.
Correct Answer
C. Convection results from a density change.Explanation
Convection occurs when there is a density change in a fluid, causing the fluid to move. This movement can be in the form of currents or circulation. Brownian motion is not a form of convection, but rather the random movement of particles in a fluid due to collisions with other particles. Convection can occur in both gases and liquids, not just in gases. Evaporation, on the other hand, is a process where a liquid changes to a gas, and it is not a form of convection.Rate this question:
-
Quiz Review Timeline +
Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.
-
Current Version
-
Mar 22, 2023Quiz Edited by
ProProfs Editorial Team -
Jun 23, 2009Quiz Created by
Yapshinn
Back to top