PHY 102 Exam 2: Chapter 5

A hair dryer uses 856 W of power. If the hair dryer is using 8 A of current, what is the voltage (in Volts) that produces this current?

107

What do charged objected feel?

A force between one another

What is a Van de Graaff generator?

A generator that uses a moving belt to accumulate electrical charge on a hallow metal globe on the top of an insulated column

A balloon will stick to a wooden wall if the balloon is charged. Hint: Wood is an insulator and doesn't conduct electricity well. A. negatively. B. positively. C. either positively or negatively. D. None of the above choices are correct.

C. either positively or negatively

The strength (or magnitude) of the electrical force between charges depends only on the charges' A. magnitude. B. separation distance. C. magnitude and separation distance. D. sign. E. None of the above choices are correct.

C. magnitude and separation distance

A positive ion has more A. electrons than neutrons. B. electrons than protons. C. protons than electrons. D. protons than neutrons. E. neutrons than protons.

C. protons than electrons

Electric charges of the same sign A. also have the same magnitude. B. attract each other. C. repel each other. D. exert no forces on each other.

C. repel each other

Partical A has twice the charge of a nearby particle B. Compared to the force on Particle A, the force on Particle B

Is the same

What does Ohm's law state?

V = IR, or I=V/R, where V is the voltage drop (electric potential drop) and I is the current (measured in amperes)

What analogy helps up understand resistance, voltage, and current?

Voltage = water pressure Current = gallons/second flowing Resistance - size of pipes (small pipes - large resistance, large pipe = low resistance

What materials gain a negative electrical charge

Wood, rubber, teflon

Large resistance = ____________ Low = resistance = ____________

difficult, easy

What do ohms measure?

resistance of electric current; how difficult it is for current to flow

What is ionization energy?

the energy required to remove an electron from an atom

What happens if you double the distance between charges to the force.

Set d'=2d and find that F'=F/4. If we separate by 3 times (r'=3d) then the force is reduced by 1/9.

A positive charge of 10 C is 2 m from a negative charge of 20 C. What is the force of one of the charges due to the other charges in units of Newtons?

-4.5 x 10^11 N

The electric and gravitation force between an electron and proton in a hydrogen atom Electron mass: 9.1 x 10 ^-31 kg Electron charge: -1.6 x 10^-19 C Proton mass: 1.67 x 10 -27 kg Proton charge: + 1.6 x 10^-10 C

-9.240^-8 N 4 x 10^-47 N

A positive charge of 10 nano-Coulombs is 2 cm from a positive charge of 20 nano-coulombs. What is the force on one of the charges due to the other charge in Newtons?

.0045 N

Charges Q1 and Q2 exert repulsive forces of 13 N on each other. What is the repulsive force in Newtons when their separation is decreased so that their final separation is 69 % of their initial separation?

27.3

A current of 1 A passes through a lamp with a resistance of 5 Ohms. What is the power supplied to the lamp in Watts?

5

What does 1 Coulomb equal?

6.3 x 10^18 electrons

What is charge?

A property of matter that can be positive or negative

What are electric fields?

A way of visualizing a system of charges

What is the effective resistance of three resistors with resistance R connected in parallel? A. 3R B. R C. R/3 D. None of these

A. 3R

Which statement is correct? A. Charge flows in a closed circuit. B. Voltage flows through an open or a closed circuit. C. Resistance flows through an open circuit. D. Current is the primary cause of voltage. E. Charge flows in either an open or closed circuit.

A. Charge flows in closed circuit

An electron and a proton A. attract each other. B. repel each other. C. neither attract nor repel each other.

A. attract each other

The electrical force between charges is strongest when the charges are A. close together. B. far apart. C. The electric force is constant everywhere. D. opposite signs. E. the same signs.

A. close together

Strip electrons from an atom and the atom becomes a A. positive ion. B. negative ion. C. different element. D. molecule. E. a neutral ion.

A. positive ion

When the distance between two charges is halved, the electrical force between the charges A. quadruples. B. doubles. C. halves. D. becomes 1/4 of the original force. E. None of the above choices are correct.

A. quadruples

Two charged particles attract each other with a force F. If the charges of both particles are doubled, and the distance between them also doubled, then the force of attraction will be A. the same. B. twice as large. C. half as much. D. 1/4 as much. E. none of these

A. the same

What is the unit for charges per second?

Ampere (A)

Electric charges of the opposite sign A. also have the same magnitude. B. attract each other. C. exert no forces on each other. D. repel each other.

B. attract each other

If you comb your hair and the comb becomes positively charged, then your hair becomes A. positively charged. B. negatively charged. C. uncharged. D. a different color.

B. negatively charged

Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles must have A. the same sign. B. opposite signs. C. the same mass. D. the same size. E. impossible to answer without additional information

B. opposite signs

A main difference between gravitational and electric forces is that electrical forces A. attract. B. repel or attract. C. obey the inverse-square law. D. act over shorter distances. E. are weaker.

B. repel or attract

The current through a 10-ohm resistor connected to a 120-V power supply is A. 1 A. B. 10 A. C. 12 A. D. 120 A. E. none of these

C. !2 A

The power dissipated in a 4-ohm resistor carrying 3 A is A. 7 W. B. 18 W. C. 36 W. D. 48 W. E. not enough information to say

C. 36 W

Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be A. F. B. 2 F. C. F/2. D. F/4. E. none of these

C. F/2

The same voltage is measured across two wires. Wire A carries twice the current of wire B. If the resistance of wire B is R, what is the resistance of wire A? A. R B. 2R C. R/2 D. 4R E. R/4

C. R/2

On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in A. parallel. B. perpendicular. C. series. D. haste.

C. series

Particle A has twice the charge of nearby particle B. Compared to the force on Particle A, the force on Particle B is A. four times as much. B. twice as much. C. the same. D. half as much. E. None of the above choices are correct.

C. the same

F = k(q1q2/d^2) k = 8.99x10^9m^2C^-2

Coulomb force between charged particles (inverse square law)

A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is A. 40 W. B. 160 W. C. 320 W. D. 12,800 W. E. none of these

D. 12,800 W

The power dissipated in each of two light bulbs is the same. The voltage across light bulb A is twice that of light bulb B. If the resistance of light bulb B is R, what is the resistance of light bulb A? A. R B. 2R C. R/2 D. 4R E. R/4

D. 4R

If 0.8 A of current flow through a light bulb connected to a 120 V outlet, the power consumed is A. 12 W. B. 15 W. C. 60 W. D. 96 W. E. 120 W.

D. 96 W

A light bulb carries a current I. The power dissipated in the light bulb is P. What is the power dissipated if the same light bulb carries a current of 3I? A. P B. 3P C. P/3 D. 9P E. P/9

D. 9P

The direction of an electric field is the direction of the force that the field would exert on A. a neutral charge. B. a negative charge. C. an atom. D. a positive charge. E. a molecule.

D. positive charge

How does force relate to charge and distance?

Directly proportional to the product of charges Inversely as the square of the separation distance

The electric power of a lamp that carries 2 A at 120 V is A. 1/6 watts. B. 2 watts. C. 60 watts. D. 20 watts. E. 240 watts.

E. 240 watts

A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? A. 5 V B. 10 V C. 15 V D. 20 V E. more than 20 V

E. more than 20 V

Opposites attract and like charges repel in terms of F?

F < 0 charges attract F > 0 then they repel

What materials gain a positive electrical charge

Glass, wool, hair, silk, leather

Can a current flow without a complete path?

No

What is the unit for resistance?

Ohms (Ω)

What do we get when we combine Ohm's law with electrical power?

P = IV with I = V/R gives P = (V/R)V, P = V^2/R P = IV with V = IR gives P = I(IR), P = I^2R

What particles have an electrical charge?

Protons, electrons, and ions

What happens if you double the distance between charges to the force?

This force looks just like the gravitational case, except gravity involved two masses and mass can only be positive!

Electrical power

electrical power = current x voltage or P=IV

A neutral atom has 22 protons in its nucleus, the number of surround electrons is

exactly 22

What are the differences between electric and gravitational force

mass can only be positive so gravitational force only attracts charge can be negative so the electric force can attract or repel magnitude of electrical force is much larger than gravity

In order to maintain a certain current when the pipe's capacity is reduced..

we have to increase the pressure