Polytechnic Physics Set 10

181. The northern end of a compass needle points approximately towards _____?

North Pole South Pole Equator None of the above

Answer: North Pole

182. The laws of reflection are true for _____?

Only plane mirrors Only concave mirrors Only convex mirrors All reflecting surfaces

Answer: All reflecting surfaces

183. For a spherical mirror with a small aperture, the radius of curvature is _____ the focal length?

Half Equal to Three times Twice

Answer: Equal to

184. A straight and enlarged image can be created by _____?

Only a convex mirror Only a concave mirror Only a plane mirror Both convex and concave mirrors

Answer: Only a concave mirror

185. When a ray of light obliquely moves from a denser to a rarer medium, it _____?

Bends away from the normal Bends towards the normal Passes straight through the normal Does not bend

Answer: Bends towards the normal

186. If the resistance of a bulb filament is 1200 Ω, how much current will an electric bulb draw from a 220 V source?

2,64,000 A 980 A 5.45 A 0.18 A

Answer: 0.18 A

187. When resistors are connected in series, the current in the circuit

Remains the same Is reduced to half Is reduced to one-fourth Doubles

Answer: Doubles

188. How much energy is given to each coulomb of charge passing through a 12 V battery?

6 J 0.83 J 0.167 J 12 J

Answer: 12 J

189. The commercial unit of electrical energy is

Kilowatt-hour Kilowatt/hour Kilowatt/(hour)² Kilowatt(hour)²

Answer: Kilowatt-hour

190. An electric iron with a resistance of 20 Ω draws a current of 5 A. The heat generated in 30 seconds is

1.5 J 1.5 x 10² J 1.5 x 10⁴ J 1.5 x 10⁶ J

Answer: 1.5 x 10⁴ J

191. In an ocean thermal power plant, the working fluid is

A volatile fluid like ammonia Petrol Charcoal Liquefied petroleum gas

Answer: A volatile fluid like ammonia

192. When there is an electric current in a straight conductor,

There are circular magnetic field lines around it Magnetic field lines parallel to the conductor No magnetic field lines None of the above

Answer: There are circular magnetic field lines around it

193. In an electric circuit, two resistors of 2 Ω and 4 Ω are connected in series to a 6 V battery. The heat dissipated by the 4 Ω resistor in 5 seconds will be

10 J 15 J 20 J 30 J

Answer: 15 J

194. The human eye forms the image of an object on its _____.

Cornea Iris Pupil Retina

Answer: Retina

195. A real magnified image, three times the size of an object placed 10 cm in front of a concave mirror, is formed. Where is the image located?

30 cm from the mirror 20 cm from the mirror 10 cm from the mirror 3.33 cm from the mirror

Answer: 30 cm from the mirror

196. When two resistors R₁ and R₂ are connected in parallel, the equivalent resistance (Rp) of the parallel combination is

Rp = (R₁ + R₂) / R₁R₂ Rp = R₁R₂ / (R₁ + R₂) Rp = (R₁ + R₂) / R₁ – R₂ Rp = (R₁ – R₂) / R₁ + R₂

Answer: Rp = R₁R₂ / (R₁ + R₂)

197. Which of the following does not represent electric power in a circuit?

I²R V²/R VI IR²

Answer: IR²

198. Magnetic field lines appear closer where the magnetic field is _____.

Stronger Weaker Uniform None of the above

Answer: Stronger

199. The device used to convert electrical energy into mechanical energy is

Galvanometer Ammeter Electric Motor Potentiometer

Answer: Electric Motor

200. The device used to convert chemical energy into electrical energy is

Diode Ammeter Potentiometer Electric Cell

Answer: Electric Cell