# Week 39 (May 20 - 24)

**Final exam on Friday 11:20 am.**

To study: here are some questions I asked on the previous quizzes.

To study: here are some questions I asked on the previous quizzes.

**Final exam**

To study:here is a pdf file of the 2023 final exam.

To study:

Also: here are some questions I asked on previous quizzes.

Also: here are some questions I asked on previous quizzes.

There is a temperature at which the reading on the Kelvin scale is numerically

(a) equal to that on on the Celsius scale

(b) lower than that on the Celsius scale

(c) equal to that on the Fahrenheit scale

(d) less than zero

(e) none of the above

An insulated container, filled with water, contains a thermometer and a paddle wheel. The paddle wheel can be rotated by an external source. This apparatus was used by Joule to determine

(a) specific heat of water

(b) relation between kinetic energy and absolute temperature

(c) thermal conductivity of water

(d) efficiency of changing work into heat

(e) mechanical equivalent of heat

Which would require the most heat energy?

(a) meltinga1gramicecubeat0degC

(b) raising the temperature of 1 gram of water from 0 deg C to 100 deg C

(c) vaporizing 1 gram of water at 100 deg C

(d) all of these take the same quantity of heat

Suppose that one mole of gas is placed in a chamber that is fitted with a movable piston. The gas is

then allowed to expanded from Vi to Vf at constant pressure Po. The work done by the gas during this expansion is

(a) Po×(Vf−Vi)

(b) nRT× lnVf/Vi

(c) nRT × ln Vi/Vf

(d) Po / (Vf −Vi )

The thermal conductivity of gold is 320 watts per meter degree celsius. Suppose that a heat current of 10 watts is conducted down a long bar of gold having a cross sectional area of 1 square cm.

6. If the length is 1 meter, then what is the temperature difference between the ends of the gold bar?

7. Suppose the bar was made of silver (instead of gold) whose thermal conductivity is about 400. Would the temperature difference between the ends be larger or smaller than your previous answer?

Magnetic field lines

(a) form closed loops always

(b) were first conceived by Michael Faraday in the mid 1800’s

(c) point from the south face toward the north face inside of a magnet

(d) indicate the direction that a compass needle will point in the vicinity of a magnetized object

(e) all of the above

Consider two charges fixed along a straight line one meter apart. The right charge has a charge of qR =+4, the left one has a charge qL =−1.

7. Make a sketch of this scenario.

8. Now suppose a third charge q3 = +2 is placed along the same line but one meter to the left of the left charge. Sketch this.

9. What is the net force acting on q3?

You have a parallel plate capacitor with a cross sectional area of 1 square centimeter. You also have a 1000 volt battery. In this problem, use the estimate that ε0 ≃ 1 × 10−11 Farads per meter.

1. Suppose you place the parallel capacitor plates 1 cm apart. If you use the battery to fully charge the capacitor, then how much charge, Q, does the parallel plate capacitor hold?

2. Now, if you disconnect the battery from the fully charged capacitor and then move the plates closer to each other, what happens? In particular, if you change the distance to 1mm, what is the electric potential difference, V , across the capacitor plates? And how much charge, Q, does the capacitor now hold?

The amplitude of the alternating voltage in a standard American wall outlet is about

(a) 120 volts

(b) 170 volts

(c) 240 volts

(d) all of the above

A circular loop of wire rotates about a diameter in a magnetic field that is perpendicular to the axis of rotation. Looking in the direction of the field at the loop, the induced current is

(a) always clockwise

(b) always counterclockwise

(c) clockwise in the lower half of the loop and ccw in the upper half

(d) clockwise in the upper half of the loop and ccw in the lower half

(e) sometimes cw and sometimes ccw

In your lab experiment last week, you set up two small mirrors on a table, placed an object between the mirrors, and observed the images that appeared behind the mirrors. In order for exactly three images to form behind the mirrors, approximately what angle did you make between the mirrors?

(a) 30 degrees

(b) 60 degrees

(c) 90 degrees

(d) 135 degrees

(e) 180 degrees

The separation of white light into colors by a prism is associated with

(a) total internal reflection

(b) partial reflection from a surface

(c) variation of index of refraction with color of light

(d) a decrease of the speed of light in the glass

(e) absorption of light by the glass

The index of refraction of liquid benzene is 1.80. The smallest angle for total internal reflection of a light beam coming from inside the liquid benzene toward the benzene-air surface is

(a) arctan(5/9)

(b) arcsin(5/9)

(c) arcsin(9/5)

(d) arctan(9/5)

(e) none of the above

A 4 cm tall object is placed 50 cm in front of a converging lens. The focal length of the lens is 10 cm.

1. Make a clear sketch of this situation.

2. What is the image distance? Draw the image in your diagram above.

3. Is the image real or virtual?

4. Is the image upright or inverted?

5. How tall is the image?

A thin coating (n = 1.25) is painted on top of a sheet of glass (n = 1.5). White light falls perpendicularly onto the thin coating.

1. What is the minimum thickness so that there is no reflected yellow (λ = 500 nm) light ?

Consider the following radioactive processes. Write down a correct nuclear decay formula, including the elements, atomic numbers and atomic weights. You may consult a periodic table of the elements to assist you.

1. Alpha-decay of Beryllium - 9.

2. Beta-decay (electron emission) of Uranium - 239.

3. Beta-decay (positron emission) of Magnesium - 23.

Bismuth - 212 undergoes alpha decay with a half life of 60 minutes. Suppose you start with a sample containing one billion atoms of bismuth-212.

1. Make a sketch of the number of parent nuclei remaining as a function of time. Be sure to clearly label your axes and write down some numbers.

What is the energy and wavelength of the photon emitted when the electron of a helium atom makes a transition from the n=4 state to the n=1 state?

Write down the electron configuration of the following elements: Lithium, Carbon, Oxygen.