physics 100 chapter 8,9

Does electricity flow across a circuit or through a circuit? Charge flows through and voltage is impressed across a circuit.

Charge flows through and voltage is impressed across a circuit.

How could a light bulb near an electromagnet, but not touching it, be lit? Is ac or dc required? Defend your answer.

If the light bulb is connected to a wire loop that intercepts changing magnetic field lines from an electromagnet, voltage will be induced which can illuminate the bulb. Change is key, so to stay lit the electromagnet should be powered with AC.

What are the three ways in which voltage can be induced in a loop of wire?Which of these does a transformer change: voltage, current, energy, power.

Move a magnet near the loop, move the loop near a magnet, change current in a nearby loop

Show that when you touch your wet fingers (resistance 1000 Ω) to the terminals of a 6-V battery, the small current moving through your fingers is 0.006 A.

Ohm's law: Amps=V/Ωso: 6/1000= 0.006 A

Does a battery produce dc or ac? Does the generator at a power station produce dc or ac?

The battery is dc; the generator is ac

When a current-carrying wire is placed in a strong magnetic field, no force acts on the wire. What is probably the orientation of the wire?

The current and the wire are pointing in the same direction (parallel) of the magnetic field, which leads to a zero degree angle, which leads to no force acting on the wire.

When the distance between a pair of charged particles increases by a factor of four, what happens to the force between them? Does it depend on the sign of the charges? What law supports your answer?

The force is reduced to 1/4 of its original value, no matter the sign of the original charges. Coulomb's law defends our answer.Work Step by Step F=kq1q2d2If d is doubled, the force is divided by a factor of 4.This statement does not depend on the value or signs of the charges q.

A strong magnet attracts a paper clip with a certain force. Does the paperclip exert a force on the strong magnet? If not, why not? If so, does it exert as much force on the magnet as the magnet exerts on it? Defend your answers.

The paper clip exerts just as much force on the magnet because of Newton's third law. The force the paper clip exerts is not as obvious because it doesn't cause the magnet to move in any way (magnet's mass is too large)

At the atomic level, what is meant by saying something is electrically charged?

When something is electrically charged, at the atomic level it either has more total electrons than protons (in which case it is negatively charged), or it has fewer total electrons than protons (in which case it is positively charged).

We know that a compass points northward because Earth is a giant magnet. Does the northward-pointing needle point northward when the compass is brought to the Southern Hemisphere?

Yes, for the compass aligns with the Earth's magnetic field, which extends from the magnetic pole in the Southern Hemisphere to the magnetic pole in the Northern Hemisphere.

Will either pole of a magnet attract a paperclip? Explain what is happening inside the attracted paper clip.

Yes. The north pole of the bar magnet lines up magnetic domains in the paper clip, in such a fashion that the domain's south pole are on the closer side. In the same way, the south pole induces north poles in the paper clip.This causes the attraction.

What is the shape of a magnetic field about a current-carrying wire?

a pattern of concentric circles.

Which has the greater electrical resistance, wet skin or dry skin?

dry skin

Which flows through an electric circuit: voltage, electric charge, resistance, or all three?

electric charge

What is meant by saying that charge is conserved?

electrons are neither created or destroyed but are simply transferred from one material to another.

All atoms have moving electric charges. Why, then, aren't all materials magnetic?

how the charge moves dictates the direction of its magnetic field. (A magnetic field is a vector quantity.) Magnetic fields cancel, more in some materials than others.

A dehumidifier with a resistance of 20 Ω draws 6.0 A when connected to an electrical outlet. Show that the power consumed by the iron is 720 W

p=I^2 =(6.0A)^2(20Ω) =720A^2Ω =720 W

How does an electrically polarized object differ from an electrically charged object?

polarized is just shifting of the atoms

How is Coulomb's law similar to Newton's law of gravitation? How is it different?

similar: both law are inverse- square laws different: gravitation is only attractive electrical forces are attractive.

What is the effect on current through a circuit of steady resistance when the voltage is doubled? What if both voltage and resistance are doubled?

the current gets stronger because the "pressure" of the voltage is larger; it stays the same because the increase of both cancel each other out

Which part of an atom is positively charged, and which part is negatively charged?

the nucleus is positively charged and the electron cloud is negatively charged.

How does the total current through the branches of a parallel circuit compare with the current through the voltage source?

the sum of the current in the branches equal the current through the source. the pathway for current from one terminal of the battery to the other is completed if only one lamp is lit. A break in any one path does not interrupt the flow of charge in the other paths.

The bulbs are identical. Ammeters are placed in different locations, as shown. Rank, from greatest to least, the current readings in the three ammeters.

they are the same

What kind of charge does an object acquire when electrons are stripped from it?

when electrons are stripped from an object, it is left with a positive charge.

Do a pair of parallel current-carrying wires exert forces on each other?

yes, each will experience a force

All bulbs are identical in the circuits. An ammeter is connected next to each battery, as shown. Rank, from greatest to least, the current readings in the three ammeters. ( a. little B. middle C. big)

A. B. C.

In a circuit consisting of two lamps connected in series, if the current in one lamp is 1 A, what is the current in the other lamp?

1A

If 6 V were impressed across the circuit in the question above, and the voltage across the first lamp were 2 V, what would be the voltage across the second lamp?

4 volts. The sum of the voltages across each lamp must add up to the total voltage both lamps.