Ch 22

The potential difference between a storm cloud and the ground is 100 million volts. If a charge of 1.2 C flashes in a bolt from cloud to Earth, what is the change of potential energy of the charge?

-PE\Q=V -PE=VxQ -PE= 100millionV X 1.2C -PE= 1.2×10 8 J

How much energy is given to each coulomb of charge that flows through a 1.5-V battery?

1.5 joules 1 volt = 1 joule/coulomb

The three pairs of metal same-size spheres have different charges on their surfaces, as indicated. Each pair is brought together, allowed to touch, and then separated. Rank from greatest to least the total amount of charge on the pairs of spheres after separation. A) +8 +2 B) +6 -2 C) +10 -2

A, C, B The total charge on the spheres will remain constant after they touch. Initially, A has 10 (8+2) units of charge, B has 4(6+-2) and C has 8(10-2) units of charge. This total will not change. A>C>B

What is meant by saying that charge is quantized?

All charged objects have a charge that is an integer multiple of the charge of an electron. There is no smaller units of charge (than one electron/proton) observed!

How does the charge of one electron compare to that of another electron? How does it compare with the charge of a proton? How do the masses of protons and electrons compare?

All electrons have the same charge. Electron charge is equal and opposite to the proton charge. A proton has 1800 times the mass of an electron.

In terms of net charge, how does an electrically polarized object differ from an electrically charged object?

An electrically polarized object can have zero net charge, while a charged object cannot have zero net charge. Polarized: one side of atom is more +, other side is more -. Charged: entire atom is either + or - charged.

Shown are three separate pairs of point charges. Assume the pairs interact only with each other. Rank the magnitudes of the force between the pairs from largest to smallest. A) -4q<---------x--------->+2q B) +3q<--------x--------->+3q C) +2q----------x/2---------->-2q

BAC

A droplet of ink in an industrial ink-jet printer carries a charge of 1.6×10−10 C and is deflected onto paper by a force of 3.4×10−4 N . Find the strength of the electric field to produce this force.

E = F/q E = 3.4 x 10^-4 / 1.6 x 10^ -10 = 2.125 x 10^-14 N/C

Given that k=9.0×109N⋅m2/C2 (the proportionality constant for Coulomb's law), select the correct equations that show that the force between the charges is 3.6×108N.

F=kq1q2/r2=(9.0×109N⋅m2/C2)⋅(0.1C)⋅(0.1C)(0.5m)2=3.6×108N F=k(q1)(q2)/ r^2 Force= k (1stcharge)(2ndcharge)/ r squared

Rank the six combinations of electric charges on the basis of the electric force acting on q1. Define forces pointing to the right as positive and forces pointing to the left as negative.

Largest +1, -1, -1 & -1, +1, +1 +1, -1, +1 +1, +1, -1 +1, +1, +1 & -1, -1, -1 Smallest

How is the direction of an electric field defined?

The direction of the field is the direction of the force on a positive test charge.

Why does the gravitational force between Earth and Moon predominate over electrical forces?

The electric force between Earth and Moon cancels out because they have an equal number of positive and negative charges.

Why are metals good conductors of both heat and electricity?

The outer shell electrons in metals are free to move from atom to atom. "loose" outer shell e-

Find the voltage change when an electric field does 7.0 J of work on a 0.00014-C charge.

ΔV = 50 kV V = E/Q = 7.0J/0.00014C =50000V

Find the voltage change when the same electric field does 14 J of work on a 0.00028-C charge.

ΔV= 50 kV V= E/Q =14J/0.00028C =50000V