Physical Science Chapter 15

In what three ways may the strength of an electromagnetically induced current be increased?

*moving the magnet more quickly *increasing the strength of the magnet *increasing the number of turns of wire in the coil

What voltage would be produced by five 9.0 V batteries arranged in parallel? In series?

*parallel - 9.0 V (same voltage as any single cell) *series - 45 V (voltages of all the cells added together)

If 5.0 C of charge flows through a wire in 0.50 s, what is the current (in amperes)?

10. A

What is the difference between a conductor and an insulator?

A conductor is material through which current flows easily; an insulator is material through which current does not flow easily.

Compare and contrast series and parallel circuits, including their effects on resistance, current, and voltage.

Answers should include the following ideas: *Ohm's law applies to both series and parallel circuits and any part of them. *In a series circuit, the loads are arranged so that the electric current flows through each load one after another; in a parallel circuit, loads are arranged in separate brances of the circuit and the current is divided among them. *In a series circuit, the resistances of the individual loads add to each other; in a parallel circuit, the total resistance is reduced as more loads are added in parallel. *In a series circuit, the amount of current remains the same throughout the circuit; in a parallel circuit, the total current flowing through the circuit increases as branches are added, although the current flowing through each load remains the same. *In a series circuit, the total voltage equals the sum of the loads' individual voltages; in a parallel circuit, the voltages of all the branches are equal.

Describe the parts and operation of an AC motor.

Answers should include the following ideas: *The main parts are the field magnet, which provides a stationary magnetic field; the armature, a rotating electromagnet; and slip rings, which keep the wires from twisting as the armature turns. *An electric current passing through the coil of the armature magnetizes the armature, giving it north and south poles. *The north pole of the armature is repelled by the north pole of the field magnet but attracted to the south pole; the south pole of the armature is repelled by the south pole of the field magnet and attracted to the north pole. *When the poles of the armature and field magnet align, the alternating current reverses, switching the armature's poles. *Magnetic attraction and repulsion cause the armature to make another half-turn; the current then switches again, and the process repeats.

What is the difference between a closed circuit and an open circuit?

Answers should include the following ideas: *closed circuit - contains a complete path for electrons to flow from the source of current, through the load, and back to the source *open circuit - contains a gap that electrons cannot cross

List the three main parts of a simple AC motor and explain the purpose of each part.

Answers should include the following ideas: *field magnet - magnet that provides a stationary magnetic field *armature - rotating electromagnet that aligns with the poles of the field magnet *slip rings - keep the wires from twisting as the armature turns

Why might it be dangerous to replace a blown-out fuse with a fuse of larger capacity?

Answers will vary but should include the idea that the larger fuse would not protect agains an overloaded circuit because it could allow more current to pass than the circuit can safely handle.

What is the main difference between direct and alternating current?

Direct current is electricity that flows in only one direction; alternating current is electricity that reverses at regular intervals.

How is power defined when dealing with electricity?

Power equals voltage times current. (P=VI)

How can Ohm's law be stated mathematically?

V = IR

What is a superconductor?

a material that allows current to flow through it with no resistance at all

What is electromagnetic induction?

ability of magnetism to convert mechanical motion into electric current

What type of small AC generator recharges the battery of a car and powers the car's electrical system when the car is running?

alternator

What unit of measurement is used to describe the amount of current?

ampere

What are three of the factors that affect the ease of current flow?

any three of the following: *type of material *diameter of conductor *length of conductor *temperature

What is a group of electrochemical cells connected together as a single source of current?

battery

What is the most important device for converting electricity into motion?

electric motor

What is a relay?

electrical switch operated by an electromagnet

Which type of light is more efficient: the incadescent lamp or the fluorescent lamp?

fluorescent lamp

What two types of devices may be used to prevent circuits from overheating because of faulty wiring, overloads, or short circuits?

fuses, circuit breakers

What is a device that uses electromagnetic induction to produce electricity?

generator

What device produces light using a filament heated to a very high temperature by electricity?

incandescent lamp

What semiconductor devices are used to emit light?

light-emitting diodes (LEDs)

What device uses electromagnets to convert pulses of electricity into sound waves?

loudspeaker

In which type of circuit are the loads arranged so that electricity is divided among the different loads?

parallel

What term describes the amount an object hinders current flow? What unit is used to measure this quantity?

resistance; ohm

What is an electrical device designed to add resistance to a circuit?

resistor

In which type of circuit are the loads arranged so that electricity has to flow through each load one after another?

series

What term refers to a dangerous situation in which electricity takes a "short cut" through a circuit, avoiding the load?

short circuit

What simple device converts electricity to back-and-forth motion?

solenoid

What are the three basic parts of a simple electric circuit?

source of current, conductors, load

What 19th century communication device used electromagnets to reproduce messages by means of audible clicks?

telegraph

What is a device that increases or decreases the voltage of an alternating current through electromagnetic induction?

transformer

What is the force with with an electric current flows?

voltage