Science Class 8th

341. Pupil of an eye is made smaller or larger by:

A) Lens

B) Cornea

C) Iris

D) Retina

342. A line passing through centre of curvature ,optical centre and principle focus is called :

A) Optical centre

B) Focal length

C) Principal axis

D) None of these

343. The camera lens form a _____ image of an object on the film.

A) Real, small and inverted

B) Virtual, small and inverted

C) Real , large and straight

D) Virtual , large and straight

344. _______ is a device that convert mechanical energy into electrical energy

A) Generator

B) Tube well

C) Pump

D) None of the above

345. The A.C generator is based on the principle of _____ induction.

A) Electromagnetic

B) Magnetic

C) Option B is correct

D) None of these

346. The electricity generated by conversion of kinetic energy of water is called ____ power.

A) Hydroelectric

B) Hydrothermal

C) Hydro chemical

D) None of the above

347. In hydroelectric power station, the potential energy of the stored water is changed into its ______ energy.

A) Kinetic

B) Thermal

C) Chemical

D) None of the above

348. _______energy of wind is converted into electrical energy by means of windmills.

A) Mechanical

B) Chemical

C) Kinetic

D) None of these

349. A ____ is a machine which converts kinetic energy of the wind into mechanical energy of the wind turbine

A) Windmill

B) Wind grinder

C) Watermill

D) None of these

350. A steady wind with a speed of about ______ is needed for generation of electricity.

A) 30 km/hr

B) 40 km/hr

C) 20 km/hr

D) None of the above

351. Generating electricity by means of heat produced by burning of fossil fuels is called ____ power.

A) Water

B) Thermal

C) Wind

D) Chemical

352. Resistor is measured in units called _____

A) Newton

B) Calories

C) Joule

D) Ohms

353. A _____ is a device that let current flow in only one direction.

A) Diode

B) Capacitor

C) Resistor

D) Transistor

354. A _____ is a device that temporarily store an electric charge.

A) Anode

B) Cathode

C) Capacitor

D) None of these

355. Capacity of capacitor is measured in _____

A) Farad

B) Joule

C) Ohms

D) None of these

356. A transistor is a device with _____ terminals.

A) Two

B) Four

C) Three

357. The current which flow only in one direction is called ____ current.

A) Alternate

B) Direct

C) Semi alternate

D) None of the above

358. The current which changes its direction is called _____ current




D. None

359. The devices that convert A.C to D.C is called _____

A) Transistor

B) Rectifier

C) Capacitor

D) None of the above

360. _____ devices change none electrical energy into electrical energy.

A) Input

B) Output

C) Processors

D) None of the above