Weber 10 15 0015web 500 0025 300 n δt ε δ δt δ n ε

weber 10 * 1.5 0.015web
500
0.025
* 300
N
Δt * ε
Δ
Δt
Δ
N ε law, s Faraday' Using
300V
0.025
10
* 0.75
Δt
ΔIp
M ε
? ? Δ ε 500, N 0.025sec, Δt 10A, 0A - 10A ΔIp H, 0.75 M : Data Given
2
s
s
      
  
      



15.7: A solenoid has 250 turns and its self-inductance is 2.4 mH. What is the flux through each turn
when the current is 2 A? What is the induced emf when the current changes at 20As -1 ?
48mV V 10 * 48 20 * 10 * 2.5
Δt
ΔI
10 * 92 . 1
250
2 * 10 * 2.5
N
LI
LI N equation Using
? ε ?, 20A/sec,
Δt
ΔI
2A, I H, 10 * 2.5 2.5mH L inductance Self 250, N : Data Given
3 - 3 -
5
3 -
3 -
   
    
       

L
web

 

15.8: A solenoid of length 8.0cm and cross sectional area 0.5cm 2 has 520 turns. Find the self-
inductance of the solenoid when the core is air. If the current in the solenoid increases through
1.5A in 0.2s, find the magnitude of induced emf in it.
volt 10 * 1.6
0.2
1.5
* 10 * 2.12
Δt
ΔI
L ε
H 10 * 2.12 10 * /8 10 * 0.5 * (520) 10 * 4 π /l)A (N μ lA (N/l) μ lA n μ L Equation Using
? ε ? L sec, 0.2 Δt 1.5A, ΔI 520, N m 10 * 0.5 0.5cm A m, 10 * 8 cm 8 l length : Data Given
3 4
4 2 4, - 2 7 - 2
o
2
o
2
o
2 -4, 2 -2
 
 
  
    
         
15.9: When current through a coil changes from 100 mA to 200 mA in 0.005s, an induced emf of 40
mV is produced in the coil. (a) What is the self-inductance of the coil? (b) Find the increase in the
energy stored in the coil.
Created in Master PDF Editor - Demo Version
Created in Master PDF Editor - Demo Version

57
mJ J E L 03 . 0 3 10 * 03 . 0 ) 10 * 100 ( 10 * 2
2
1
) (
2
1
E
2mH H 10 * 2
0.005
0.1
3 - 10 * 40
t
I
L
? E stored energy in Increase ? L inductance Self
0.005sec Δt V, 10 * 40 40mV ε A, 10 * 100 100mA - 200mA ΔI 200mA, I 100mA, I : Data Given
2 3 3 2
3 -
3 -3
2 1
      
  



    
      
 


15.10: Like any field, the earth’s magnetic field stor es energy. Find the magnetic energy stored in a
space where strength of earth’s fields is
T
5
10 7


, if the space occupies an area of
2 8
10 10 m 
and has a height of 750m.
J AL
B
Um
Um m L
o
9 8
7
5 - 2
2 8 -5
10 * 5 . 1 ) 750 * 10 * 10 (
10 * 4
2 ) 10 * (7
2
1
) (
2
1
? , 750 , m 10 * 10 A T, 10 * 7 B : Data Given
  
   
  
15.11: A square coil of side 16cm has 200 turns and rotates in a uniform magnetic field of
magnitude 0.05T. If the peak emf is 12V, what is the angular velocity of the coil?
47rad/sec c 46.9rad/se
0.05 * 10 * 256 * 200
12
NAB
ε
ω N ωωA ε
? ω 12V, ε 0.05T, B 200, N , m 10 * 256 16cm * 16 A Area 16cm, coil square of Side : Data Given
4 -
o
o
o
2 -4 2
     
       
15.12: A generator has a rectangular coil consisting of 360 turns. The coil rotates at 420 rev per min
in 0.14 T magnetic field. The peak value of emf produced by the generator is 50V. If the coil is 5.0 cm
wide, find the length of the side of the coil.
0.45m
0.05 * 43.96 * 360 * 0.14
50
bB N ω
ε
L
b)B * N ωω( N ωωA ε formula the using ? L coil of length
0.05m 5/100 5cm b width 50V, ε 0.14T, B rad/sec, 43.96
60
2 π * 420
ω 360, N : Data given
o
o
o
  
   
        
15.13: It is desired to make an a.c generator that can produce an emf of maximum value 5kV with 50
Hz frequency. A coil of area 1m 2 having 200 turns is used as armature. What should be the
magnitude of the magnetic field in which the coil rotates?