161. Electric current in a metal wire is due to the flow of –
1. Electrons
2. Protons
3. Ions
4. Holes
Option “1” is correct. An electric current is a flow of electric charge which is often carried by moving electrons.
162. The nature of fuse wire is –
1. Low melting point
2. High melting point
3. High conductivity
4. None of these
Option “1” is correct. Electric fuse is a protective device which protects electrical equipment in the circuit by breaking the circuit when there is a short circuit.It has low melting point.
163. A transformer –
1. converts DC to AC
2. is used to decrease or increase AC voltage
3. converts AC voltage to DC voltage
4. converts electrical energy into mechanical energy
Option “2” is correct. A transformer is used to bring voltage up or down in an AC electrical circuit.
164. Which one of the following is the unit of measure of the thickness of the ozone layer of the atmosphere?
1. Knot
2. Dobson
3. Poise
4. Maxwell
Option “2” is correct. Ozone layer thickness is expressed in terms of Dobson units, which measure, what its physical thickness would be if compressed in the earth’s atmosphere. 1 Dobson unit is defined to be 0.01 mm thickness STP (Standard Temperature and Pressure).
165. The density of milk can be obtained by the use of:
Option “3” is correct. Lactometer is used for the measurement of the density of milk. Butyrometer is used to measure fat content in milk or milk products.
166. It is difficult to walk on the ice than on the road because:
1. Ice is harder than the road.
2. Road is harder than the ice.
3. Ice does not offer any reaction when we push it with our foot.
4. Ice has a lesser friction than the road.
Option “4” is correct. It is very difficult to walk on the ice than on the road because ice has a lesser friction than the road. The roughness of road’s surface gives you much frictional force which enables you to move forward on road.
167. Static science is associated with-
1. Dynamic situation
2. Situation of rest
3. Mental situation
4. Data analyzing
Option “2” is correct. Statics is a branch of mechanics associated with the situation or rest.
168. The colour of the star is an indication of its:
1. Distance from the earth
2. Temperature
3. Luminosity
4. Distance from the sun
Option “2” is correct. The colour of the stars reflects the age of stars. Colour is reflected from the temperature is high, then the star is young. The star will be blue during young stage which indicates high temperature. If star is red the temperature is low.
Option “1” is correct. The power of the sunglass is 0 dioptre.
170. A pendulum clock can run faster in-
1. Summer
2. Winter
3. Spring season
4. Rainy season
Option “2” is correct. A pendulum clock runs faster in winter because in winter the length of the pendulum or the swing become smaller due to contraction and the clock begin to run fast.
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