Page 7 - ECAT Past Paper 2006

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Q.25 A small parallel resistance (shunt) used to convert galvanometer into an ammeter of
suitable range is given by:
A) Rs= ∗ B) Rs= ∗ (Correct)
+ −
C) Rs= + ∗ D) Rs= −
−
-Self Explanatory.
For your information:
1) Range of an Ammeter: Rs=
−1
2) Range of a Voltmeter: Rh=(n-1) Rg
Q.26 Permeability of free space is given by:
-7
-7
A) 4π*10 Wb/Am (Correct) B) 1/4π *10 Wb/Am
-3
C) 2π*10 Wb/Am D) None of these
-Self Explanatory.
Q.27 An inductor of 1 henry is connected across a 220 V,50 Hz supply. The peak value of
current is:
A) 0.5 A B) 0.7 A
C) 1 A (Correct) D) 1.4 A
Explanation:
As we know that:
XL=2πf L
XL=2*3.14*50*1
=100*3.14
=314 Ohm
We also know that:
Irms=Vrms/XL
Irms= 220/340
Irms=0.70 A
As we are to find the peak value of current so:
Irms= Io/√2
0.70*√2=Io
Io= 0.9899 A
Io=1 A (Approx)
Q.28 Transistor is basically a:
A) Voltage amplifier (Correct) B) Current amplifier
C) Rectifier D) None of these
Explanation: As we know that the gain of amplifier is given by:
A=-βRc/rie
The value of the factor βRc/rie is of order of hundred so the input voltage is amplified thus
transistor is basically a voltage amplifier.
Q.29 Hydrogen is also called
A) Deuterium B) Tritium
C) Protium D) All of these (Correct)
-Self Explanatory.
Q.30 Rate of decay of radio active element ____ with time:
A) increases B) decreases (Correct)
C) remains same D) All of these
Explanation:
As we know that:
−∆ /
:. =
∆
As t increases so that rate of decay decreases
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