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
A. AC
B. DC
C.Ampere
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