The secondary coil of a large transformer near the street supplies your home with 120-volt alternating current. The transformer's primary coil has 50 times as many turns as its secondary coil. At this moment, the transformer is supplying electric power only to your home and that power is 6000 watts. The transformer's primary coil is being supplied with

The electrons in an atom reside in orbitals. Those orbitals are best described as

The north pole of a strong permanent magnet is moved rapidly toward the surface of a huge copper block. What force, if any, does the permanent magnet experience as it approaches the copper block?

Two round chocolates, one of which weighs twice as much as the other, roll off a horizontal table side-by-side at the same moment and the same initial velocity. In this situation,

Tasha and Chloe are carrying 25-pound sacks of flour from the sidewalk to your 10th floor bakery, 100 feet above the sidewalk. Tasha carries sacks up the stairs. Chloe carries sacks up a vertical ladder. Compare the work each person does on a sack while moving it from the sidewalk to the bakery. [Neglect friction and air resistance, and assume that sacks are motionless at the start and finish.]

The radioactive atoms produced by nuclear fission are hazardous to humans. Why can't these atoms be rendered safe by burning them in an incinerator?

The power outlet in your room supplies 120-volt alternating current. That outlet has two metal slots through which power is provided. One slot is longer than the other. Which of the following statements is true about those two metal slots?

The windshield of a car has three layers: two layers of glass and a layer of clear, tear-resistant plastic in between. The index of refraction of that plastic is almost identical to the index of refraction of the glass. What would happen if the plastic's index of refraction were twice that of the glass?

Gamma rays are used in radiation therapy to treat cancer. One of the ways in which a gamma ray damages tumor cells is by producing an electron out of empty space. To avoid creating or destroying a conserved quantity, what else does the gamma ray produce?

A battery charger recharges a battery by

When an electric current flows through a thin vapor of sodium atoms, the discharge emits a pure yellow light. As the density of the sodium vapor increases, the color of the discharge becomes more of a yellow-tinted white light. What causes this change in color?

An n-channel MOSFET transistor consists of a piece of p-type semiconductor separating two pieces of n-type semiconductor. It also has a gate that controls the flow of electric current through the MOSFET. What change in the gate allows current to flow through the MOSFET?

Most digital devices use binary symbols to represent information. How many different numbers can be uniquely represented using 4 binary symbols?

What happens when a CD (compact disc) is placed in a microwave oven and the oven is turned on for about 4 seconds?

Running on soft dry sand is exhausting, so you switch to running on hard wet sand. The hard wet sand takes less energy from you because

You toss an apple directly upward and watch it rise to its peak height. At the moment that it reaches that peak height, its velocity is

The color of light produced by a light-emitting diode (LED) depends on

The Chernobyl reactor was a carbon-moderated thermal fission reactor. During the Chernobyl reactor accident, ordinary water meant to cool the reactor boiled and escaped from the reactor core. Why did the disappearance of water from the reactor core allow the core's chain reaction rate to skyrocket?

You have two flashlights, one that emits red light and one that emits green light. If you overlap the beams from those two flashlights on a white surface and vary their brightnesses, which colors can you see in the region of their overlap?

You are watching children play at the local swimming pool. Two children jump off the side of the pool at the same time. They both jump equally hard, but the girl jumps mostly upward while the boy jumps mostly forward. After they leave the side of the pool,

A xerographic copier uses a very thin wire with a large positive voltage to spray electric charges onto the surface of its photoconductor. The thin wire

An LED (a light-emitting diode) emits light when an electron that has crossed the pn-junction from the

An n-type semiconductor naturally has some electrons in its conduction band of quantum levels. A p-type semiconductor naturally has some empty levels in its valence band. When an n-type semiconductor touches a p-type semiconductor, in the absence of any external electric field, what happens at the junction between the semiconductors?

Two sheets of almost perfectly flat glass are stacked together so their surfaces are extremely close to one another. When illuminated with pure green light, the reflection from this stack of glass exhibits a complicated pattern of bright and dark regions. What effect is causing those variations in the reflected brightness?

A high-quality optical fiber traps light in its transparent glass core by encasing that core in a cladding material. What is that cladding material?

A tank circuit consists of a capacitor and an inductor connected to one another electrically. A capacitor can store energy in its electric field and an inductor can store energy in its magnetic field. Suppose a tank circuit contains a large amount of energy. At the moment when the magnetic field in its inductor is at maximum strength, what percentage of the tank circuit's total energy is in its capacitor?

A neon atom has 10 electrons in orbitals around its atomic nucleus. When the neon atom is in its ground state (having no extra energy), how many different orbitals do those 10 electrons occupy?

Modern astronomical telescopes use mirrors with enormous diameters. In addition to gathering large amounts of light, a large-diameter mirror

A radioactive nucleus has a half-life of 10 days, so it has a 50% chance of surviving the next 10 days. You wait for 10 days and find that the nucleus has survived that first 10-day period. Now what is the chance that the nucleus will survive another 10-day period?

During a head-on collision between cars, the front ends of those cars crumple strategically. Why is it helpful to have the front end of a car—the portion under the car's hood—crush to a shorter length during a head-on collision?

The nucleus of an ordinary hydrogen atom is a single proton. That proton has a

Frozen food cooks slowly in a microwave oven until it defrosts. Once it has defrosted, it cooks quickly. What slows the microwave cooking in frozen food?

The constituents of a radioactive nucleus are in stable equilibrium, yet they eventually rearrange in a way that allows the nucleus to fall apart and release stored energy. What allows the nucleus to escape from its stable equilibrium and subsequently fall apart?

A metal wall has been built to stop a transmitter's radio wave from reaching your receiver (see figure). The wall has two holes, but those holes are shifted well away from the path between transmitter and receiver. Despite the wall, however, the radio wave still reaches your receiver. Why?

As a wave of sunlight travels through empty space on its way to the earth, that light wave consists of

An n-type semiconductor naturally has some electrons in the levels of its conduction band. What can an engineer do to convert a piece of pure semiconductor into n-type semiconductor?

In analog representation, a single physical quantity represents another single physical quantity. For example, the voltage of a wire can represent the pressure of a musical sound and carry that sound information to a distant speaker system. What is the primary shortcoming of representing musical sound as the voltage of a wire?

A magnifying glass is a converging lens that can form real images, just like a camera lens. You hold a magnifying glass 5 inches from the wall of your room and it forms a sharp image on the wall of the window at the other side of the room. There is a tree outside the window. To form a sharp image of the tree on the wall, you must move the magnifying glass

When two fluorescent cards are exposed to ultraviolet light, Card A emits blue light and Card B emits red light. When those cards are exposed to green light, what will the cards do?

A metal conducts electricity because

A diode is a junction between an n-type semiconductor and a p-type semiconductor. When an electric field acts to push electrons toward the junction on the p-type side and away from the junction on the n-type side,

When a patient is having an X-ray image taken of an injured wrist, that patient wears a lead apron to protect the rest of the body. What characteristic of lead allows it to absorb X-rays so effectively?

You are on an exercise machine and grip its handles as they move back and forth. Suppose you exert a 10-newton force on the handle as it moves away from you. How does the direction of the force you exert on the handle affect the work you do on the handle as the handle moves away from you?

You hold a positively charged stick near an electrically neutral glass ball. You then hold the stick near an electrically neutral metal ball. The stick never touches either ball. What force does the charged stick experience in these two cases?

A sharp metal pin has a voltage of +1000 volts and it points toward a wide metal surface with a voltage of –1000 volts (see figure). What is the voltage midway between the surface and the pin?

You are camping, but you still want to blow-dry your hair. When a wire in your 2-mile extension cord is carrying a current of 10 amperes, it experiences a voltage drop of 5 volts. When your friend turns on a second hairdryer and the same wire is carrying a current of 20 amperes, the wire then experiences a voltage drop of

For a nuclear reactor to maintain a chain reaction without using a moderator, it must enrich its fuel to be nearly pure uranium-235. Why would leaving uranium-238 in the fuel make it harder or even impossible to maintain a chain reaction?

Why is it energy-inefficient to transmit power long distances as large currents in two wires having a small difference in voltage?

A racquetball court has rigid, immovable walls. You hit the rubber ball forward, toward the front wall of the court, and the ball bounces back at you. Before hitting the wall, the ball carried both energy and forward momentum. During its bounce, the ball transferred to the wall

A DVD player uses a red diode laser to read the disk, whereas a Blue-ray player uses a blue diode laser to read the disk. Switching from a red laser to a blue laser allows the Blu-ray disk to hold far more information than a DVD. What is it about blue light that allows for the increase in data storage?

A normal rainbow is red on the outside of the arc, violet on the inside of the arc. What would have to be different for the color sequence to be reversed: red on the inside, violet on the outside?

Which of the following produce magnetic fields?

You are sitting in the lobby of a hotel, watching 4 people who are wearing backpacks. Which person is doing work on their backpack at this moment?

The lenses of eyeglasses can be made from a variety of different plastics. One choice is high-index plastic—a plastic with an unusually high refractive index. What are the advantages/disadvantages of using this plastic in eyeglass lenses?

The two most important 3-dimensional medical imaging techniques are CT scans (computerized X-rays) and MRI (magnetic resonance imaging). What are those two techniques best at imaging?

High-quality camera lenses often contain two different types of glass. Having two different types of glass in one lens

You are troubleshooting a complicated electrical system and you have found a black box with only two wires attached to it. How can you figure out if that box is consuming electric power?

For a portrait photograph, you want only your subject to be in focus. The background should be blurry. What type of camera lens will allow you to take such a portrait photograph?

How does a laser produce a single intense light wave?

A plastic bottle sits on an insulating counter. You are wearing a rubber glove. Both the bottle and glove are electrically neutral. You grip the bottle briefly and, when you let go of it, your glove is negatively charged. As you move the glove away from the bottle, the voltage of the glove