2019-03-01_Physics_Times

An alternating current of frequency ' 'f is flowing

in a circuit containing a resistance R and a choke L

in series. The impedance of this circuit is

(a) R^2  4 2 2 2f L (b) R 2 fL

(c)

R^2  2 fL (d) 2 2

R L

A step - up transformer operates on a 230V line and

supplies a load of 2 ampere. The ratio of the primary

and secondary winding is 1 : 25. The current in the

primary is

(a) 25A (b) 50A

(c) 12.5A (d) 15A

Identify the gate represented by the block diagram

as shown in fig.

(a) AND gate (b) NOT gate

(c) NAND gate (d) NOR gate

a b a d d

a b d c d

b c a d b

d a a a c

b b a d a

a a d a c

d d d a c

b b d a b

b c a b d

Let xM L Ta b c

100 100

X a M b L c L

X M L T

     

    

 

    a b c %

Given that v=10-5t

The average velocity is

2

0 (10 5)

2 0

t dt

v









2 2

0 0

1

10 5 ) 5 /

2

v   dt t dt m s

  

Let v be the river velocity and u the velocity of

swimmer in still water. Then

(^12) 2 2
W
t
u v
 
  
  
2 2 2
W W 2 uW
t
u v u v u v
  
  
and 3
2 W
t
u

Now we can see that t1 2 3^2 t t
Radial acceleration
2 2
(30) 1.8 2
500
r
v
a ms
r
   
Tangential acceleration at  2 m/sec^2
Resultant acceleration
2 2 2 2 cos
a   ar at a att 
Here   90
a^2 (1.8) (2) 0 3.24 4 7.24^2     ^2
a 7.24 2.7 ms^2
Let gravitational field is zero at a distance x from
the mass M.
 
 
2 2
GM G^4 M
x r x


 
2 2
   4 x r x
2 x r x^
3
r
 x
The potential at that point is
^4 
p
GM G M
V
x r x
   

3 6GM GM 9 GM
r r r
    
Assume that the total mass M is present at
infinity. We bring the total mass and form like a
sphere. Let m is the mass of the shell having radius
R. To bring further mass dm from infinity the work
done by the external agent is
ext f i R
1.Sol:
2.Sol:
3.Sol:
4.Sol:
5.Sol:
6.Sol:
dW     dU U U U U
ext
Gm Gmdm
dW dm
R
 
  
  
2
(^02)
M
ext
G GM
W mdm
R R
 

  