Review Exercise

Part 1: Review

n One amp is the amount of current that flows in a conductor when one ____________ of charge

moves past a point in one second. coulomb

n List the 2 basic types of cells below

Ø ________________________________

primary and secondary

n The text discussed the 6 most common voltage sources. List these sources.

Ø ________________________________

friction, magnetism, chemical, light, heat, pressure

n What is the name of the instrument used to measure

Ø Resistance: ________________________________ Ohmmeter

Ø Current: ___________________________________ Ammeter

Ø Voltage: ___________________________________ Voltmeter

n What is the name of the instrument that can measure all of the above?______________________ multimeter

n A resistor's ______________________ is the amount that it may vary and still be acceptable. tolerance

n For each of the following, indicate whether the instrument is connected in series with the item being measure or in parallel (your answer should be either series or parallel).

Ø Resistance: ________________________________ Parallel

Ø Current: ___________________________________ Series

Ø Voltage: ___________________________________ Parallel

n A way to measure current that does not require opening the circuit is to use a resistor of known value in the circuit. Such a resistor is called a (an) ___________

ammeter shunt.

n The testing for an open, closed, or short circuit is called a _____________________ check. continuity

n List the 2 types of ground discussed in the text.

Ø ________________________________

earth, electrical

n _________________ produces the energy to dislodge electrons from their orbit. voltage

n Resistors are either __________________ or __________________ fixed, variable

n Variable resistors used to control voltage are called _____________________ potentiometers

n Variable resistors used to control current are called _________________ rheostats

n The unit of difference of potential is named in honor of Allessandro _________________ Volta

n The unit of current is named after Andre-Marie ______________________________ Ampere

n The total current flowing into a junction is equal to the sum of the current flowing out of the junction. This is a statement of __________________________ current law. Kirchoff's

n The basic unit of power is the ____________________________ watt

n The sum of all the voltage drops in a closed circuit will equal the voltage source. This is a statement of ________________________ voltage law. Kirchoff's

n What is the current in amps if 15 coulombs of current flows past a point in an electric circuit in 5 seconds?

3 coulombs/second = 3 amps

n Given the following circuit. Each resistor has a value of 2 ohm (1 ohm on some - answer changed accordingly).

Ø This is an example of a

__________________circuit

series

Ø The total resistance, RT, is

________________________________

R1 + R2 + R3 + R4 = 8 ohms

n Given the following circuit. Each resistor has a value of 1 ohm.

Ø This is an example of a

__________________circuit

parallel

Ø The total resistance, RT, is

______ (R1R2R3)/(R2R3 + R1R3 +

R1R2) = 1/3

n Given the following circuits, designated as circuit a and circuit b. Each battery supplies 6 V and 500

mA.

Ø What is the total voltage in circuit a?________ 12 V

Ø What is the total voltage in circuit b?________ 6 V

n How much current is used by a 100-watt, 120 volt light bulb?

P = IE

100 = I(120) gives I = 100/120 = 0.83 amp or 5/6 amps

n Given that a current of 0.5 amp flows through a 20 ohm resistor, how much power is dissipated by

the resistor?

V = IR = 0.5x20 = 10 volts

P = VI = 10x0.5 = 5 watts

n How much power is consumed in the following circuit. The unmarked resisor, R2, is 820 ohms

We first find the total resistance for the circuit which, because the resistors are in series, is just the total of the individual resistors: R_total = R1 + R2 + R3 = 560 + 820 + 1000 = 2380 ohms

With the total resistance we can find the total current flowing in the circuit using Ohm's law.

Itotal = ETotal/RTotal = 12/2380 = 0.005 amps.

The total power can now be determined. P = IE = 0.005x12 = 0.06 watts

Part 2: Magnetism

n A ________________________ consists of invisible lines of force that surround a magnet. magnetic field

n The invisible lines of force above are referred to as _________________ lines flux

n _________________________ is the effect a magnet has on an object without physical contact. Magnetic induction

n A ________________ is an electromechanical switch that opens and closes with an electromagnetic coil. relay

n The strength of an electromagnet is directly proportional to:

ð ____________________________________ Number of turns in the coil

ð ____________________________________ Amount of current flowing through the coil.

n ____________________ law states that the inducted voltage is directly proportional to the rate at which the conductor cuts the magnetic lines of force. Faraday's

n For electromagnetic induction to occur, either the magnetic field or the conductor must move. The voltage produced in the conductor is called ________________ voltage.

induced

n In an AC generator the rotating loop is called a (an) __________________________. armature

n A DC generator converts mechanical energy to electrical energy, similar to an AC generator except that it converts the AC voltage to DC voltage. It does this with a device called a

_________________ commutator.

n An AC generator converts mechanical energy to electrical energy by utilizing the principle of ______________ induction. electromagnetic

Part 3: Inductance

n The letter symbol _____________ represents inductance. L

n The unit of inductance is the _______________. Henry

n The letter symbol ___________represents the unit of inductance. H

n Draw the schematic symbol a fixed inductor in the space below.

n Draw the schematic symbol for a variable inductor below.

Same as above with an arrow though it pointed up and to the right.

n Given three inductors with inductances L₁, L₂, and L₃.

ð If conducted in series, the total inductance L_T = L₁ + L₂ + L₃.

ð If conducted in parallel, the total inductance L_T = L₁L₂L₃/(L₂L₃ + L₁L₃ + L₁L₂)

n An LR ______________________________ is the time required for current through a conductor to increase to 63.2% or decrease to 36.8% of the maximum current.

time constant

n Inductance is a measure of the resistance to a change in _______________ current

n ______________ are devices that store energy in a magnetic field. Inductors

n List the equation used to find the time constant, t, for an RL circuit. t = L/R L = inductance in henries, R is resistance in ohms

n An induced emf in any circuit is always in a direction to oppose the effect that produced it. his is a statement of ______________________ law. Lenz's

Part 4: Capacitance

n The letter symbol ____________represents capacitance. C

n The unit of capacitance is the ____________Farad

n The letter symbol ____________ represents capacitance. F

n Draw the schematic symbol for a fixed capacitor in the space below.

n Draw the schematic symbol for a variable capacitor in the space below.

Same as above with an arrow though it pointed up and to the right.

n I displayed a device in class a number of times that was one of the first attempts at building what is now called a capacitor. It is called a _________________________ jar.

Leyden

n Given three capacitors with capacitances C1, C2, and C3

ð If conducted in series, the total capacitance C_T = C₁C₂C₃/(C₂C₃ + C₁C₃ + C₁C₂) or 1/C_T = 1/C₁ + 1/C₂ + ...

ð If conducted in parallel, the total capacitance C_T = C₁ + C₂ + C₃.

n Four factors that affect the capacitance of a capacitor are

ð ____________________________________ Area of the plate

ð ____________________________________ Distance between the plates

ð ____________________________________ Type of dielectric material

ð ____________________________________ Temperature

n An RC __________________________ reflects the relationship between time, resistance, and capacitance. time constant

n Capacitance is a measure of the resistance to a change in _______________ voltage

n Write the formula for the RC circuit time constant below.

t = RC