Page 6 - ECAT Past Paper 2006

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C) 4 (Correct) D) 5
Explanation:
A typical four petrol engine also undergoes four successive processes in each cycle.
Q.20 Speed of sound in Vacuum is ---- m/s.
A) 332 B) 340
C) 0 (Correct) D) 350
Explanation:
Speed of Sound for:
 Air: 332 m/s
 Vacuum: 0 m/s
 Oxygen: 315 m/s
Q.21 When effective value of current is 10.What is its peak value?
A) 12 B) 13
C) 10 D) 14.1 (Correct)
Explanation:
As we know that:
I rms=Io/√2
Irms=10
so; 10*√2=Io
Io=1.41*10
Io=14.1 A (Answer)
st
Q.22 A body moves with the uniform acceleration with a distance x for 1 second and y for
next 4 seconds then what is relation b/w x and y?
A) y=24x B) y=16x (Correct)
C) y=12x D) y=8x
Explanation:
As we know that:
2
S= vit+ ½ at
as body movies with uniform acceleration so vi=0
so S= ½ at
2
2
Let it be x and y ½ at for some interval .
2
2
For 1 second: x= ½ at  x= ½ a(1) x= ½ a ---(1)
st
For 4 second: y= ½ at y= ½ a(4)  y=16 (½ a)—(2)
th
2
2
As we are to find the relation b/w x and y so:
From (2)  y= 16x (Answer)
Q.23 An electron volt is equal to:
-12
-12
A) 0.62*10 J B) 1.6*10 J
12
C) 0.62*10 J D) 1.6*10 J (Correct)
-19
-Explanation:
18
1 J=6.25*10 eV
-19
1eV= 1.6*10 J
-1
Q.24 A wire 3.0 m long, of uniform cross section area 2.0 mm has a conductance 1.25 ohm ,
2
What is resistivity of material of the wire.
A) 5.3*10 ohm-m (Correct) B) 2.15 ohm-m
-7
-7
-7
C) 8.3*10 ohm-m D) 1.9*10 ohm-m
Explanation:
Given data:
L=3.0 m
2
A=2 mm or 2*10 m
2
-6
-1
G= 1.25 so R=1/G R=1/1.25 R=8*10 ohm
As we know that:
p= RA/L
-1
-6
p= 8*10 *2*10 /3
-7
p=5.3*10 ohm-m (Answer)