The threshold of frequency for photoelectric effect depends on the
Aintensity of incident light
Bfrquency of incident light
Cmaterial of the photocathode
Dpotential difference between the cathode and the anode
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Question 1912
jamb1992
In A.C circuit theory, the root means square (r.m.s) current, Irms and the peak (maximum)current Io are related by
AIo = \(\frac{I_rms}{\sqrt{2}}\)
BIrms = \(\frac{I_o}{\sqrt{2}}\)
CIrms = \(\frac{\frac{I}{I_o}}{\sqrt2}\)
DIrms = \(\frac{I_rms}{\sqrt{2}}\)
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Question 1913
jamb1992
In alternating current theory, the units of impedance, r.m.s. voltage and resonance frequency are respectively equal to
Avolt, ampere and hertz
Bohms, volt and hertz
Cwatt, ohms and radian
Dohms, hertz and joule
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Question 1914
jamb1992
The maximum permissible current through a galvanometer G of internal resistance 10\(\Omega\) is 0.05A. A resistance R is used to convert G into a voltmeter with a maximum reading of 100V. Find the value of R and how it is connected to G
A20,000 ohms in parallel
B19,990 ohms in series
C1990 ohms in series
D100 ohms in series
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Question 1915
jamb1992
The heat produced in a conductor carrying an electric current is
Ainversely proportional to the current and the resistance
Bdirectly proportional to the current, resistance and the time
Cinversely proportional to of the resistance, current and the time
Ddirectly proportional to the square of the current, the resistance and the time
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Question 1916
jamb1992
Which of the following apparatus will require the smallest fuse rating for its protection?
A60W, 240V
B60W, 40V
C40W, 12V
D40W, 5V
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Question 1917
jamb1992
A 5-v battery is connected across the plates of a 2.0\(\mu\)F uncharged parallel plate capacitor. The charge on the capacitor after a long time is
A2.5\(\mu\)C
B10.0\(\mu\)C
C20.0\(\mu\)C
D50.0\(\mu\)C
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Question 1918
jamb1992
A wire of length 15m made of a material of resistivity 1.8 x 10-6\(\Omega\)m has a resistance of 0.27\(\Omega\). Determine the area of the wire
A1.5 x 10-4m2
B1.0 x 10-4m2
C2.7 x 10-5m2
D7.3 x 10-6m2
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Question 1919
jamb1992
Which of the following factors has no effect on the e.m.f. of a primary cell?
Atemperature
Bsize of the cell
Cnature of the plate
Dnature of the electrolyte
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Question 1920
jamb1992
When an ebolite rod is rubbed with fur, it has
Ano charge at all
Ba negative charge
Ca positive charge
Dnegative and positive charges
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Question 1921
jamb1992
Calculate the force acting on an electron of charge 1.6 x 10-19C placed in an electric field of intensity 108Vm-1
A1.6 x 10-11N
B1.6 x 10-14N
C1.6 x 10-16N
D1.0 x 10-16N
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Question 1922
jamb1992
The angle between the direction of the earth's magnetic field and the horizontal is called the
Aangle of deviation
Bmagnetic declination
Cmagnetic meridian
Dangle of dip
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Question 1923
jamb1992
Which of the following arrangements of the components of electromagnetic spectrum is in ascending order of wavelengths?
AGamma rays, ultraviolet rays, X- rays, infra - red rays
If the refractive index of a medium in air is 2.0, what is the critical angle for this medium?
A30o
B42o
C45o
D50o
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Question 1925
jamb1992
The speed of light in air is 3 x 10\(^8\)ms\(^{-1}\). What is the speed in glass with a refractive index of 1.50?
A1.5 x 108ms-1
B3.0 x 108ms-1
C2.0 x 108ms-1
D6.0 x 108ms-1
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Question 1926
jamb1992
Which of the following statements is CORRECT about a long-sighted boy who does not put on glasses?
AHe cannot see distant objects clearly
BRays of light from a close object are focused in front of his retina
CHis eye ball is too long
DParallel rays of light are focused behind his retina
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Question 1927
jamb1992
A concave mirror has a radius of curvature of 36cm. At what distance from the mirror should an object be placed to give a real image three times the size of the object?
A12cm
B24cm
C48cm
D108cm
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Question 1928
jamb1992
When an object is placed very close to the pole of a concave mirror, the virtual image obtained is
Adiminished and upright
Bdiminished and inverted
Cenlarged and inverted
Denlarged and upright
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Question 1929
jamb1992
Which of the following properties make the convex mirror useful as a driving mirror? i. the image is real. ii. the image is erect. iii. it has a wide field of view. iv. the image is magnified.
Ai, ii, and iv
Bi, ii, iii
Cii and iii
Di and iii
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Question 1930
jamb1992
What is the frequency of the sound made by a siren having a disc with 32 holes and making 25 revolution per seconds?
