# Ocean Energy Questions and Answers – Tidal Energy – 2

This set of Ocean Energy online quiz focuses on “Tidal Energy – 2”.

1. What is a tidal lagoon?
a) A man-made structure that spans the area of coastline with a high tidal range
b) A man-made structure that spans the entire coastline
c) A barrage
d) A fast-flowing water body caused due to tides

Explanation: A tidal lagoon spans that area of coastline which has a high tidal range. The large volume of water is collected in a man-made structure for electricity generation. Tidal stream is a fast-flowing water body caused due to tides.

2. How does a tidal lagoon work?
a) By storing sea water
b) By creating a difference in water levels
c) By placing the turbine in the running water
d) By creating barrages

Explanation: Tidal lagoon works by creating a difference in water levels. The water on the higher level is passed through a turbine to generate electricity. Tidal barrages work by creating barrages.

3. Which of the following steps best describes the working of tidal lagoons?
a) Floods → generator turbines → turbine wicket gates → lagoon → difference in water level between lagoon and sea
b) Floods → turbine wicket gates → generator turbines → lagoon → difference in water level between lagoon and sea
c) Floods → turbine wicket gates → lagoon → difference in water level between lagoon and sea → generator turbines
d) Turbine wicket gates → floods → lagoon → difference in water level between lagoon and sea → generator turbines

Explanation: Sea water flows into lagoons which are controlled by turbine wicket gates. These gates control the flow and can be completely closed to stop the water from entering the lagoon. Once the difference in the water level between lagoon and sea is optimized, the gates are opened thereby allowing water to flow through generator turbines.

4. Tidal lagoon is _______
a) unidirectional
b) unpredictable
c) the same as tidal stream
d) bi-directional

Explanation: Tidal lagoon is bi-directional. This is because the difference in water level between the lagoon and sea can be created by both, the incoming tides and the outgoing (ebbing) tides.

5. Tidal power is renewable because _________
a) tide falls and rises without fuel
b) tide falls and rises with fuel
c) tide neither falls nor rises without fuel
d) tide neither falls nor rises with fuel

Explanation: The tidal power is renewable because the tides fall and rise without any external fuel. This is caused by the gravitational forces of moon and earth’s rotation.
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6. How many high tides occur every day?
a) One
b) Two
c) Four
d) Three

Explanation: Two high tides occur each day. This is because the earth rotates through two tidal bulges every lunar day. When the earth is in one of the bulges, coastal areas experience a high tide.

7. How many low tides occur every day?
a) One
b) Five
c) Two
d) Four

Explanation: Two low tides occur each day. This is because the earth rotates through two tidal bulges every lunar day. When the earth is not in one of the bulges, a low tide occurs.

8. On which two sides of the earth do the tidal forces cause water to bulge out?
a) Both sides closest to moon
b) Both sides farthest from moon
c) Both sides facing the sun
d) Side closest to the moon and farthest from the moon

Explanation: Tides are caused by the gravitational forces of moon acting on earth. Side closes to the moon and sides farthest from the moon bulge out due to these tidal forces.

9. Bulges of water are called high tides.
a) True
b) False

Explanation: Bulges of water are called high tides. The two earth’s sides namely, the one closest to the moon and the one farthest from the moon experience these bulges – high tides.

10. What is a tide mill?
a) A dam to store the tide
b) A water mill driven by tidal rise and fall
c) A barrage
d) A lagoon

Explanation: A tide mill is a water mill driven by tidal rise and fall. A dam is created across a tidal inlet to store the water thereby acting as a reservoir. A tidal mill is not same as a dam.

11. How does a tide mill work?
a) By storing the water and creating a difference in water level
b) By storing the water when the tide is low and releasing it through a turbine when the tide is high
c) By storing the water when the tide is high and releasing it through a turbine when the tide is low
d) By using the running water of a tide

Explanation: The tide mill works by storing the water when the tide is high and releasing it through a turbine when the tide is low. The water is stored in a dam constructed across a suitable tidal inlet.

12. Which of the following is similar to the working of tidal stream generator?
a) Geothermal turbine
b) Heat pump
c) Anaerobic digestion
d) Wind turbine

Explanation: The working of tidal stream generator is similar to that of a wind turbine. Both use the kinetic energy of the respective fluids to rotate the turbine and generate electricity. Anaerobic digestion is a technique to treat and harness energy from biomass. It does not used turbines. Geothermal turbine and heat pumps use the thermal energy of the fluids.

13. Both horizontal and vertical turbines are used to harness energy from tides.
a) True
b) False

Explanation: Depending on the tidal stream various turbines are used to harness the kinetic energy of the incoming tide. Some of the commonly used turbines are horizontal, vertical, open and ducted.

14. What is dynamic tidal power?
a) A theoretical technology exploiting potential energy of tides
b) A theoretical technology exploiting potential and kinetic energy of tides
c) A practical technology exploiting kinetic and potential energy of tides
d) A practical technology exploiting thermal energy of tides

Explanation: Dynamic tidal power is a theoretical technology that exploits an interaction between the potential and kinetic energy of tides. It proposes the construction of long dams from coast into the sea so as to introduce tidal phase differences. These phase differences result in a differential water-level.

15. Strong coast-parallel oscillating tidal currents are found in ______
a) India
b) United States
c) China
d) Australia

Explanation: Strong coast-parallel oscillating tidal currents are generally found in China, UK and Korea. Dynamic tidal power (DTP) is a theoretical technology that features such currents and proposes harvesting energy from such currents.

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