NCERT Class 11 Geography — Chapter 2: Movements of Ocean Water

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Which one of the following is NOT a primary force initiating ocean currents?

Official previous-year question

Verified 1 Aug 2026.

Options

AHeating by solar energy
BGravity
CDifferences in water density
DPrevailing winds

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Solution

The correct option is C.

Explanation

Ocean currents are categorized into two types based on the forces that drive them: primary forces that initiate the movement of water and secondary forces that influence the direction and flow of the currents. Primary forces include solar heating, gravity, wind, and the Coriolis force.

Option A: Heating by solar energy (Correct): Solar heating causes water to expand. Near the equator, the ocean water level is approximately 8 cm higher than in middle latitudes. This slight gradient causes water to flow down the slope, initiating movement.
Option B: Gravity (Correct): Gravity acts as a primary force by pulling water down the gradient created by solar expansion or surface accumulation. It also plays a role in the vertical movement of water masses.
Option D: Prevailing winds (Correct): Wind blowing on the surface of the ocean exerts friction, pushing the water forward. This is a dominant primary force in the initiation of surface currents.
Option C: Differences in water density (Incorrect): Density differences, caused by variations in temperature and salinity, are classified as secondary forces. While they drive the deep-ocean vertical circulation (thermohaline circulation), they are responsible for the movement of water rather than the initial horizontal initiation of surface currents.

Key Takeaway: Primary forces (Solar heating, Wind, Gravity, Coriolis force) initiate the movement of ocean water, while secondary forces (Density differences, Temperature gradients) influence the vertical movement and speed of the currents.

Your note

More from Chapter 2: Movements of Ocean Water

Consider the following factors: 1. The shape of bays and estuaries has no influence on the magnitude of tides. 2. Presence of wide continental shelves. 3. Presence of mid-oceanic islands. Which of the above factors can influence the height or magnitude of tidal bulges?

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Which of the following best describes the general movement of warm ocean currents?

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With reference to the movements of ocean water, consider the following statements: 1. Ocean currents represent the horizontal motion of water while tides represent the vertical motion. 2. In waves, the water moves ahead from one place to another along with the wave train. 3. The upwelling of cold water from the subsurface is a form of horizontal motion. Which of the statements given above is/are correct?

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Consider the following statements regarding the characteristics of ocean waves: 1. The largest waves are typically found in open oceans rather than enclosed seas. 2. Steep waves are generally old and originate from far away places. 3. Slow and steady waves usually originate from far away places. Which of the statements given above is/are correct?

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The maximum height of a wave is determined by which of the following factors? 1. The strength of the wind has no role in determining wave height. 2. The duration for which the wind blows. 3. The area over which the wind blows in a single direction. Select the correct answer using the code given below:

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The correct option is C.

Explanation

Option A: Heating by solar energy (Correct): Solar heating causes water to expand. Near the equator, the ocean water level is approximately 8 cm higher than in middle latitudes. This slight gradient causes water to flow down the slope, initiating movement.
Option B: Gravity (Correct): Gravity acts as a primary force by pulling water down the gradient created by solar expansion or surface accumulation. It also plays a role in the vertical movement of water masses.
Option D: Prevailing winds (Correct): Wind blowing on the surface of the ocean exerts friction, pushing the water forward. This is a dominant primary force in the initiation of surface currents.
Option C: Differences in water density (Incorrect): Density differences, caused by variations in temperature and salinity, are classified as secondary forces. While they drive the deep-ocean vertical circulation (thermohaline circulation), they are responsible for the movement of water rather than the initial horizontal initiation of surface currents.