Q&A Hero

Q: The magnetic fields of a pair of nearby magnets can A) only add. B) cannot add or subtract. C) add or subtract by vector rules.

Q: An iron rod becomes magnetic when A) opposite ions accumulate at each end. B) its atoms are aligned. C) the net spins of many of its electrons are aligned. D) its electrons stop moving and point in the same direction. E) none of the above

Q: Magnetic field strength about a magnet is strongest where magnetic field lines are A) closer together. B) straightest. C) most curved. D) more spread.

Q: The conventional direction of magnetic field lines outside a magnet are from A) north to south. B) south to north. C) either way

Q: Magnetism is due to the motion of electrons as they A) move around the nucleus. B) spin on their axes. C) both of these D) neither of these

Q: Magnetic fields are produced by A) a tiny fraction of moving electrical charges. B) most moving electrical charges. C) all moving electrical charges.

Q: Surrounding every moving electron is A) a magnetic field. B) an electric field. C) both of these D) neither of these

Q: Surrounding every stationary electron is A) a magnetic field. B) an electric field. C) both of these D) neither of these

Q: Surrounding every magnet is A) a magnetic field. B) an electric field. C) both of these D) neither of these

Q: If you break a bar magnet in half you'll A) destroy its magnetic properties. B) have two magnets. C) have two and a half magnets. D) none of the above

Q: Refrigerator magnets are typically A) short range. B) long range. C) none of these

Q: Whereas electric charges can be isolated, magnetic poles A) can also. B) cannot. C) gather in clusters. D) none of the above

Q: In general, a common magnet has A) one pole. B) at least two poles. C) only two poles.

Q: Like kinds of magnetic poles repel while unlike kinds of magnetic poles A) attract. B) repel also. C) may attract or repel.

Q: The force that acts between a pair of magnetic poles depends on A) magnetic pole strength. B) separation distance. C) both of these D) neither of these

Q: The force that acts between a pair of electrically-charged particles depends on A) magnitude of charge. B) separation distance. C) both of these D) neither of these

Q: The source of all magnetism is A) tiny pieces of iron. B) tiny domains of aligned atoms. C) ferromagnetic materials. D) moving electric charge. E) none of the above

Q: Magnetic compasses reportedly were first used for navigation by A) Aristotle. B) Australian aborigines. C) Chinese sailors. D) none of the above

Q: Electric resistance in our skin is lowered when our skin is A) moist. B) dry. C) none of the above

Q: Ohm's law tells us that the amount of current produced in a circuit is A) directly proportional to voltage. B) inversely proportional to resistance. C) both of these D) neither of these

Q: When you turn on a lamp, the initial current in its filament is greater at first, rather than a moment later, which indicates A) something is faulty. B) a time delay for current attaining its average speed. C) increased temperature means increased resistance. D) nothing of interest

Q: Two light bulbs are connected to a battery, one at a time. The bulb that draws more current has the A) lower resistance, and is brightest. B) lower resistance, but is dimmer. C) higher resistance, and is brightest. D) higher resistance, but is dimmer. E) none of the above

Q: If you stretch a copper wire so that it is thinner, the resistance between its ends A) decreases. B) remains unchanged. C) increases.

Q: Heat a copper wire and its electric resistance A) decreases. B) remains unchanged. C) increases.

Q: If two copper wires of the same length have different thickness, then the thicker wire has A) more resistance. B) less resistance. C) both the same

Q: The current produced by voltage in a circuit is impeded by A) electric barriers. B) closed switches. C) electric resistance. D) none of the above

Q: The unit of electrical resistance is the A) volt. B) ampere. C) ohm. D) none of the above

Q: A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with A) 6 ohms. B) 6 amperes. C) 6 joules. D) 6 watts. E) 6 newtons.

Q: It is correct to say that in electric circuits A) charge flows through a circuit. B) flowing charge is current. C) voltage is applied across a circuit. D) voltage is the ratio of energy per charge. E) all of the above

Q: Which statement is correct? A) charge flows in a circuit B) voltage flows in a circuit C) resistance flows in a circuit D) all of the above

Q: A suitable electric pump in an electric circuit is a A) chemical battery. B) generator. C) both of these D) neither of these

Q: Electrons flow in a wire when there is A) an imbalance of charges in the wire. B) a potential difference across its ends. C) a difference in potential energy across its ends. D) none of the above

Q: Voltage is most similar to A) pressure. B) current. C) resistance. D) all of the above E) none of the above

Q: An ampere is a unit of electric A) current. B) voltage. C) resistance.

Q: To think of electric potential difference we are thinking about A) current. B) voltage. C) resistance.

Q: Just as a sustained flow of water in a hydraulic circuit needs a pump, in electric circuits the flow of charge needs A) current. B) voltage. C) resistance.

Q: Just as in hydraulic circuits there is water pressure, in electric circuits there is A) current. B) voltage. C) resistance.

Q: Just as water flows from a region of high pressure to a region of low pressure, electric charge flows from a region of A) high electric pressure to a region of low electric pressure. B) high potential energy to a region of low potential energy. C) deep to shallow regions. D) all of the above

Q: Three resistors take the shape of a triangle, one resistor in each leg. Resistance in one leg is 4 ohms, 6 ohms in a second leg, and a third leg 10 ohms. Connecting an ohm-meter across the 10-ohm resistor will show the equivalent resistance to be A) 1.4 ohms. B) 5 ohms. C) 6.7 ohms. D) greater than 6.7 ohms.

Q: Three 10-ohm resistors take the shape of a triangle, one resistor in each leg. Connecting an ohm-meter across any two points of the triangle will show the equivalent resistance to be A) 1.4 ohms. B) 5 ohms. C) 6.7 ohms. D) greater than 6.7 ohms.

Q: A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of A) 2.4 ohms. B) 4 ohms. C) 5 ohms. D) 5.5 ohms. E) 10 ohms.

Q: The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about A) 0.06 ohm. B) 1 ohm. C) 1.8 ohms. D) 6 ohms. E) 9 ohms.

Q: The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about A) 1 ohm B) 1.8 ohms. C) 6 ohms. D) 9 ohms.

Q: When a pair of 1-ohm resistors are connected in series, their equivalent (combined) resistance is 2 ohms, and when connected in parallel is A) ohm. B) none of the above C) also 2 ohms.

Q: The equivalent resistance of any series of resistors in a circuit is A) often less than the resistance of the lowest resistor. B) always less than the resistance of the lowest resistor. C) usually half the value of the lowest resistor. D) none of the above

Q: The equivalent resistance of any parallel branch in a circuit is A) often less than the resistance of the lowest resistor. B) always less than the resistance of the lowest resistor. C) usually half the value of the lowest resistor. D) none of the above

Q: To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will be least, connect them in A) series. B) parallel. C) either of these

Q: To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will increase, connect them in A) series. B) parallel. C) either of these

Q: Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? A) touching the light fixture B) touching the generator C) touching both are about equally dangerous.

Q: As more lamps are connected in a parallel circuit, the overall current in the power source A) increases. B) decreases. C) stays the same.

Q: As more lamps are connected in a series circuit, the overall current in the power source A) increases. B) decreases. C) stays the same.

Q: Sometimes the current in lamps is too feeble to produce glowing of the lamp filaments, which occurs when A) too many lamps are connected in series. B) too many lamps are connected in parallel. C) too much current is drawn by the battery.

Q: A circuit breaker often serves the same purpose as a A) battery B) fuse. C) capacitor. D) all of the above E) none of the above

Q: The safety fuse in an electric circuit is connected to the circuit in A) series. B) parallel. C) either series or parallel.

Q: Connect a pair of lamps in series and current is drawn from the battery. Connect the same lamps in parallel and the current drawn is A) less. B) the same. C) more. D) sometimes more, sometimes less.

Q: Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry A) more current. B) less current. C) the same current.

Q: Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry A) more current. B) less current. C) the same current.

Q: Modern automobile headlights are connected in A) parallel. B) a perpendicular orientation. C) series. D) none of the above

Q: On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in A) parallel. B) perpendicular. C) series. D) haste.

Q: When a pair of identical lamps are connected in parallel A) voltage across each is the same. B) current in each is the same. C) power dissipated in each is the same. D) all of the above

Q: When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is A) more than the resistance of either lamp. B) less than the resistance of either lamp. C) none of these

Q: When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A) more than the resistance of either lamp. B) less than the resistance of either lamp. C) none of these

Q: In a circuit powered by a battery, charge A) flows through the battery. B) is energized by the battery. C) both of these D) neither of these

Q: By convention, the direction of current in a circuit is A) from the positive terminal of a source to the negative terminal. B) the direction in which positive charge flows. C) both of these D) neither of these

Q: If you wish to keep chicken warm in a shed on a cold night, the best lamp to use is A) an incandescent lamp. B) a fluorescent lamp. C) an LED lamp. D) a CFL lamp.

Q: Compared with the amount of current in the filament of a lamp, the amount of current in the connecting wires is A) definitely less. B) often less. C) actually more. D) the same. E) incredibly, all of the above

Q: The amount of current in an LED bulb rated 10.5W 120V is A) less than 1 A. B) about 1 A. C) more then 1 A.

Q: The amount of current in an incandescent bulb rated 75W 120V is about A) 0.4 A. B) 0.6 A. C) 1.2 A. D) more than 1.2 A.

Q: The amount of current in a CFL rated 23W 120V is about A) 0.2A. B) 5.2A. C) more than 5.2A.

Q: A lamp rated 23W 120V means that it will deliver 23 W A) when the voltage across it is 120 V. B) whether or not it is connected to 120 V. C) as long as the current is ac. D) none of the above

Q: The brightness of a lamp is directly related to its A) brand. B) place of manufacture. C) power rating. D) all of the above E) none of the above

Q: A heater draws 20A when connected to a 110-V line. If the electric power costs 20 cents per kilowatt hour, the cost of running the heater for 10 hours is A) $0.44. B) $1.10. C) $4.40. D) $11.00. E) none of the above

Q: An electric heater is rated 300W 110V. The safety fuse in the circuit can withstand 15 A of current. How many heaters can be safely operated in the circuit? A) 2 B) 3 C) 4 D) 5 E) more than 5

Q: The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is A) 6 ohms. B) 12 ohms. C) 18 ohms. D) none of the above

Q: A 60-W and a 100-W light bulb are connected in parallel to a 120-V outlet. Which bulb draws more current? A) 60-W bulb B) 100-W bulb C) both the same.

Q: A 60-W and a 100-W light bulb are connected in series to a 120-V outlet. Which bulb draws more current? A) 60-W bulb B) 100-W bulb C) both the same.

Q: A 60-W and a 100-W light bulb are rated at 120V. Which bulb has a higher resistance? A) 60-W bulb B) 100-W bulb C) both the same.

Q: 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) need more information

Q: A lamp rated at 120W 120V has a filament resistance of A) 1 ohm. B) 60 ohms. C) 100 ohms. D) 144 ohms. E) none of the above

Q: A power line with a resistance of 2 ohms carries a current of 80 A. The power dissipated in the line is A) 40 W. B) 160 W. C) 320 W. D) 12,800 W. E) none of the above