# High Voltage Engineering Questions and Answers – Sphere Gaps

This set of High Voltage Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Sphere Gaps”.

1. Sphere gap is used for the measurement of peak value of _________
a) ac voltage
b) dc voltage
c) impulse voltage
d) ac, dc and impulse voltage
View Answer

Answer: d
Explanation: Sphere gap is used for the measurement of peak value of ac, dc and impulse voltage. It is also used for the checking of voltmeters. It finds major use in high voltage testing devices.

2. Two _________ spheres separated by a certain distance form a sphere gap.
a) identical metallic
b) identical non-metallic
c) non-identical metallic
d) non-identical non-metallic
View Answer

Answer: a
Explanation: Two identical metallic spheres separated by a certain distance form a sphere gap. Sphere gap is used for the measurement of peak value of ac, dc and impulse voltage. It is also used for the checking of voltmeters. It finds major use in high voltage testing devices.

3. Spherometer is used to measure the _________ of the sphere.
a) radius
b) diameter
c) curvature
d) radius and diameter
View Answer

Answer: c
Explanation: Spherometer is used to measure the curvature of the sphere. Two identical metallic spheres separated by certain distance form a sphere gap. Sphere gap is used for the measurement of peak value of ac, dc and impulse voltage.
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4. The spheres are placed in horizontal configuration for smaller size.
a) True
b) False
View Answer

Answer: a
Explanation: The spheres are placed in horizontal configuration for smaller size. The spheres are placed in vertical configuration for larger size. In this condition, the lower sphere is grounded.

5. The diameter of the spark gaps used in the impulse generator circuit is _________
a) 2-5cm
b) 5-10cm
c) 10-25cm
d) 25-50cm
View Answer

Answer: c
Explanation: The structure of the spark gaps is usually spherical or hemispheres. The diameter of the spark gaps used in the impulse generator circuit is 10-25cm. All the spark gaps are aligned and the capacitors are placed vertically.

6. The gap length between the sphere should exceed the sphere radius.
a) True
b) False
View Answer

Answer: b
Explanation: The gap length between the sphere should not exceed the sphere radius. Sphere gap is used for the measurement of peak value of ac, dc and impulse voltage. It is also used for the checking of voltmeters. It finds a major use in high voltage testing devices.

7. Spheres used for the spark gaps are made up of _________
a) copper
b) brass
c) aluminium
d) copper, brass or aluminium
View Answer

Answer: d
Explanation: Spheres used for the spark gaps are made up of copper, brass or aluminium. Aluminum is mostly preferred due to its low cost.
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8. The flashover occurs near the _________
a) lower spray points
b) flashover point
c) sparking point
d) middle level spray points
View Answer

Answer: c
Explanation: The flashover occurs near the sparking point. Hence the spacing between the sphere gaps is designed in such a way that flashover occurs near the sparking point. The curvature of the sphere must be uniform.

9. The spark over voltage is reduced in the presence of nearby earthed objects.
a) True
b) False
View Answer

Answer: a
Explanation: The spark over voltage is reduced in the presence of nearby earthed objects. The other factors that influence the sparking voltage are atmospheric conditions, irradiation and rise time of voltage waveforms.
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10. What is the shape of the high voltage electrode?
a) rectangular
b) triangular
c) oval
d) spherical
View Answer

Answer: d
Explanation: The shape of the high voltage is spherical. It is made with re-entrant edges to avoid corona and local discharges. The spherical shape can also avoid high surface field gradients.

Sanfoundry Global Education & Learning Series – High Voltage Engineering.

To practice all areas of High Voltage Engineering, here is complete set of Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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