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Worksheets17B Electric fields
Total questions: 15
Worksheet time: 7mins
Which of the following is a statement of Coulomb’s law?
Like charges repel and unlike charges attract.
The force between two point charges is directly proportional to the product of the charges and inversely proportional to their distance apart.
For an a-particle approaching a gold nucleus, at distance of closest approach, the kinetic energy of an a-particle is converted electric potential energy.
The force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of their distance apart.
What is electric field?
force per unit positive charge
region of space where a charge experiences a force
region of space where a particle experiences a force.
work done per unit charge in bring a positive charge from infinity to the point.
The electric field strength of a point charge Q at a distance r from the charge is
E=4πϵorQ
E=4πϵor2Q
E=4πϵoQr
E=Q4πϵor
A gold nucleus of radius r is represented by the symbol (_79^197)Au. The charge on the nucleus may be considered to be concentrated at the centre of the nucleus.
Taking e as the elementary charge and εo as the permittivity of free space, what is the electric field strength at the surface of an isolated gold nucleus?
4πϵor279e
4πϵor279e2
4πϵor2197e
4πϵor2197e2
In discussing electric fields, the terms ‘electric field strength’, ‘electric potential’ and potential gradient’ are used.
Which statement about these terms is correct?
Electric field strength at a point is the work done in bring unit positive charge from infinity to the point.
Electric potential and potential gradient are both scalar quantities.
The potential gradient at a point in numerically equal to the electric field strength at that point.
Unit potential gradient exists between any two points, if one joule of work is done in transporting one coulomb of charge between the points.
Which of the following is not true about electric potential at a point a distance r from a charge?
work done per unit positive charge, in moving charge from infinity to the point.
potential at infinity is taken as zero
work is got out of it
the potential at a point a distance r from charge Q is given as V=4πϵorQ
The radius r of the sphere is 2.4 cm. The magnitude of the charge q on the sphere is 0.76nC.
Use the expression V=4πϵorQ to calculate a value for
the magnitude of the potential V at the surface of the sphere.
2.85 V
285 V
5940 V
11900 V
Values of gravitational potential are always negative whereas values of electric potential may be positive or negative. Which of the following statement is incorrect?
gravitational forces are always attractive
electric forces can be attractive or repulsive
for gravitational, work done as masses come together
for electric, work done on charges if same sign, work got out if opposite sign as charges come together
The electrons in a cathode-ray tube are accelerated from cathode to anode by a potential difference of 2000 V.
If this p.d. is increased to 8000 V, the electrons will arrive at the anode with
twice the kinetic energy and four time the velocity
four times the kinetic energy and twice the velocity.
four times the kinetic energy and sixteen time the velocity.
sixteen times the kinetic energy and four time the velocity.
1.37 × 107 ms–1
1.0 × 107 ms–1
9.6 × 107 ms–1
1.37 × 106 ms–1
α-particle and gold nucleus repel each other,
all kinetic energy of α-particle converted into electric potential energy when α-particle comes to rest.
the gold nucleus emits gamma rays to stop the a-particle .
the distance of closest approach would be the radius of the nucleus if energy of a-particle is sufficient.
7.68 × 10-13 J
3.0 × 1025J
3.33 × 10-26 J
7.68 × 10-19 J
2.9 × 10-14 m
4.7 × 10-14 m
4.7 × 10-11 m
2.9 × 10-5 m
7.5 × 10-13 N
1.6 N
16 N
75 N
I, III
II, IV
I, IV
II, III
