Exam 15: Electric Forces and Electric Fields

A charge,+Q,is placed inside a balloon and the balloon is inflated.As the radius of the balloon r increases the number of field lines going through the surface of the balloon:

Electric field is dimensionally equivalent to which of the following?

If a conductor is in electrostatic equilibrium near an electrical charge:

An electron with a speed of 3 × 10⁶ m/s moves into a uniform electric field of 600 N/C that is parallel to the electron's motion.How long does it take to bring the electron to rest? (me = 9.11 × 10−³¹ kg,e = 1.6 × 10−¹⁹ C)

Two point charges are placed along a horizontal axis with the following values and positions: +3.6 µC at x = 0 cm and −7.1 µC at x = 40 cm.At what point along the x axis is the electric field zero? ​

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:

An initially uncharged hollow metallic sphere with radius of 5 cm has a small object with a charge of +10 µC carefully placed at the center of the sphere through a hole in the latter's surface.What charge resides inner surface of the sphere?

An airplane is flying through a thundercloud at a height of 2,500 m.(This is a very dangerous thing to do because of updrafts,turbulence,and the possibility of electric discharge. )If there is a charge concentration of +31 C at height 4,000 m within the cloud and −31 C at height 500 m,what is the magnitude of the electric field E at the aircraft? (k_e = 8.99 × 10⁹ N·m²/C²)

An initially uncharged hollow metallic sphere with radius of 6 cm has a small object with a charge of +19 µC carefully placed at the center of the sphere through a hole in the latter's surface.With the charge in place,what charge is now present on the outside surface of the sphere? ​

An electron is sent at high speed toward a gold nucleus (charge +79e).What is the electrical force acting on the electron when it is 3.4 × 10−¹⁴ m away from the gold nucleus? (e = 1.6 × 10−¹⁹ C,k_e = 8.99 × 10⁹ N·m²/C²) ​

In Millikan's oil drop experiment,if the electric field between the plates was of just the right magnitude,it would exactly balance the weight of the drop.Suppose a tiny spherical oil droplet of radius 1.3 × 10−⁴ cm carries a charge equivalent to one electron.What electric field is required to balance the weight? (The density of oil is 0.85 g/cm³,e = 1.6 × 10−¹⁹ C. ) ​

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

Relative distribution of charge density on the surface of a conducting solid depends on:

Charge A and charge B are 3.12 m apart,and charge A is +1.49 C and charge B is +3.37 C.Charge C is located between them at a certain point and the force on charge C is zero.How far from charge A is charge C? ​

Two identical spheres each carry a charge of −47.1 µC.The spheres are separated by a distance of 1.74 m.What is the electric force between the spheres? (k_e = 8.99 × 10⁹ N·m²/C²) ​

Three equal positive charges are placed on the x-axis,one at the origin,one at x = 2 m,and the third at x = 6 m.Of the following points,which has the greatest magnitude electric field? ​

The Millikan oil-drop experiment demonstrated that:

A proton initially moves left to right long the x axis at a speed of 9 × 10³ m/s.It moves into an electric field,which points in the negative x direction,and travels a distance of 0.8 m before coming to rest.If the proton's mass and charge are 1.67 × 10−²⁷ kg and 1.60 × 10−¹⁹ C respectively,what is the magnitude of the electric field? ​

A metallic object holds a charge of −5.3 × 10−⁶ C.What total number of electrons does this represent? (e = 1.6 × 10−¹⁹ C is the magnitude of the electronic charge. )

Two electrons are separated by 4 cm.What is the ratio of the electric force to the gravitational force between them? (m_e = 9.11 × 10−³¹ kg,k_e = 8.99 × 10⁹ N⋅m²/C²,G = 6.67 × 10^-11 N⋅m²/kg²,and e = 1.6 × 10−¹⁹ C) ​