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Answer: c
Explanation: The electric field intensity is the force per unit charge on a test charge, i.e, q1 = 1C. E = F/Q = Q/(4∏εr2).
Answer: c
Explanation: Force is the product of charge and electric field.
F = q X E = 2 X 1 = 2 N.
Find the electric field intensity of two charges 2C and 1C separated by a distance 1m in air.
Answer: b
Explanation: F = q1q2/(4∏εor2) = 2 X 9/(10^{9} X 12) = 18 X 10^{9}
E = F/q = 18 X 10^{9}/2 = 9 X 10^{9}.
What is the electric field intensity at a distance of 20cm from a charge 2 X 10^{6} C in vacuum?
Answer: c
Explanation: E = Q/ (4∏εor2)
= (2 X 10^{6})/(4∏ X εo X 0.2^{2}) = 450,000 V/m
Determine the charge that produces an electric field strength of 40 V/cm at a distance of 30cm in vacuum(in 108C)
Answer: a
Explanation: E = Q/ (4∏εor^{2})
Q = (4000 X 0.3^{2})/ (9 X 10^{9}) = 4 X 10^{8} C.
The field intensity of a charge defines the impact of the charge on a test charge placed at a distance. It is maximum at d = 0cm and minimises as d increases. State True/False
Answer: a
Explanation: If a test charge +q is situated at a distance r from Q, the test charge will experience a repulsive force directed radially outward from Q. Since electric field is inversely proportional to distance, thus the statement is true.
Electric field of an infinitely long conductor of charge density λ, is given by E = λ/(2πεh).aN. State True/False.
Answer: a
Explanation: The electric field intensity of an infinitely long conductor is given by, E = λ/(4πεh).(sin α2 – sin α1)i + (cos α2 + cos α1)j
For an infinitely long conductor, α = 0. E = λ/(4πεh).(cos 0 + cos 0) = λ/(2πεh).aN.
Electric field intensity due to infinite sheet of charge σ is
Answer: d
Explanation: E = σ/2ε.(1 cos α), where α = h/(√(h^{2}+a^{2}))
Here, h is the distance of the sheet from point P and a is the radius of the sheet. For infinite sheet, α = 90. Thus E = σ/2ε.
For a test charge placed at infinity, the electric field will be
Answer: c
Explanation: E = Q/ (4∏εor^{2})
When distance d is infinity, the electric field will be zero, E= 0.
In electromagnetic waves, the electric field will be perpendicular to which of the following?
Answer: c
Explanation: In an electromagnetic wave, the electric field and magnetic field will be perpendicular to each other. Both of these fields will be perpendicular to the wave propagation.
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