Physics 2 test 3

Which of the following statements are true? Check all that apply. The resistance of a conductor is proportional to the conductivity of the material of which the conductor is composed. Good conductors of electricity have larger conductivity values than insulators. Semiconductors have resistivity values that are larger than those of insulators. The resistance of a conductor is proportional to the resistivity of the material of which the conductor is composed. A material that obeys Ohm's law reasonably well is called an ohmic conductor or a linear conductor.

Good conductors of electricity have larger conductivity values than insulators. The resistance of a conductor is proportional to the resistivity of the material of which the conductor is composed. A material that obeys Ohm's law reasonably well is called an ohmic conductor or a linear conductor.

current formula in a AC cicuit

I=I0*sin(wt)

What happens to the resistance of most common metals as the temperature of the metal increases? The resistance decreases as temperature increases. The resistance remains constant as temperature increases. The resistance increases as temperature increases. Whether resistance increases or decreases as temperature increases depends on the type of metal.

The resistance increases as temperature increases.

Four unequal resistors are connected in a parallel circuit. Which one of the following statements is correct about this circuit? The total resistance is equal to zero. The total resistance is less than the smallest resistor. The total resistance is more than the largest resistor. The total resistance is equal to average of the four resistors. None of the other answers is correct.

The total resistance is less than the smallest resistor.

If the resistance in a circuit connected to a constant current is halved, how is the voltage in the circuit affected? The voltage is reduced by a factor of 2. The voltage remains constant. The voltage is reduced by a factor of 4. The voltage is quadrupled. The voltage is doubled.

The voltage is reduced by a factor of 2.

Four equal resistors connected across a DC voltage source in either series or parallel will have equal voltage drops across each resistor.

True

Consider two copper wires with the same cross-sectional area. Wire A is twice as long as wire B. How do the resistivities and resistances of the two wires compare? Check all that apply. Wire A and wire B have the same resistivity. Wire B has twice the resistance of wire A. Wire A and wire B have the same resistance. Wire A has twice the resistivity of wire B. Wire A has twice the resistance of wire B. Wire B has twice the resistivity of wire A.

Wire A and wire B have the same resistivity. Wire A has twice the resistance of wire B.

The potential difference between the terminals of a battery, when no current flows to an external circuit, is referred to as the emf terminal voltage

emf

Kirchhoff's second rule

loop rule -sum of the changes in potential around any closed loop must be zero

emf

potential difference between the terminals of a source that transfers one type of energy to another -cursive E -measured in volts

When resistors are connected in series, the same power is dissipated in each one. the current flowing in each is the same. the potential difference across each is the same. More than one of the given answers is true. None of the given answers are true.

the current flowing in each is the same.

Kirchhoff's junction rule is a statement of Newton's second law. the law of conservation of charge. the law of conservation of angular momentum. the law of conservation of momentum. the law of conservation of energy.

the law of conservation of charge.

When resistors are connected in parallel, we can be certain that the potential difference across each is the same. the same current flows in each one. their equivalent resistance is greater than the resistance of any one of the individual resistances. the power dissipated in each is the same.

the potential difference across each is the same.

Circuits in parallel formulas

I=I1+I2+I3 1/Req=1/R1+1/R2+1/R3

Terminal voltage formula

Vab=emf-Ir

electric current

the flow of charge I measured in A (ampere)

Which of the following statements are true? Check all that apply. Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time. When an electric field is applied to a conductor, the free electrons move only in the direction opposite the applied electric field. By convention, the direction of a current is taken to be the direction of flow for negative charges. In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges. In a circuit, current is delivered by the positive terminal of a battery, and it is used up by the time it returns to the negative terminal of the battery.

Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time. In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges.

current formula

I=Q/t

Which of the following will increase the resistance of a wire? Check all that apply. Decreasing the length of the wire will increase the resistance of the wire. Decreasing the resistivity of the material the wire is composed of will increase the resistance of the wire. Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. Decreasing the cross-sectional area of the wire will increase the resistance of the wire. Increasing the cross-sectional area of the wire will increase the resistance of the wire. Increasing the length of the wire will increase the resistance of the wire.

Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. Decreasing the cross-sectional area of the wire will increase the resistance of the wire. Increasing the length of the wire will increase the resistance of the wire.

Four unequal resistors are connected in a series circuit. Which one of the following statements is correct about this circuit? The total resistance is more than the largest resistor. The total resistance is equal to any one of the resistors. The total resistance is less than the smallest resistor. The total resistance is less than the largest resistor. The total resistance is equal to average of the four resistors.

The total resistance is more than the largest resistor.

As more resistors are added in series to a constant voltage source, the power supplied by the source decreases. decreases for a time and then starts to increase. does not change. increases for a time and then starts to decrease. increases.

decreases

resistivity formula

pt=p0[1+a(T-T0)] a=temperature constant

The potential difference between the terminals of a battery, when current flows to an external circuit, is referred to as the emf. terminal voltage.

terminal voltage

If the voltage across a circuit of constant resistance is doubled, how is the current in the circuit affected? The current is doubled. The current is reduced by a factor of 4. The current is reduced by a factor of 2. The current is quadrupled. The current remains constant.

The current is doubled.

time constant equation

t=RC

RC circuits

-have a resistor and capacitor -change in time

resistivity

-p -Ohms*m -something with a high resistivity is a poor conductor

A series circuit is a current divider and a parallel circuit is a voltage divider circuit.

False

An RC circuit is connected across a DC voltage source through an open circuit and a switch. As soon as the switch is closed, the charge on the capacitor increases but the voltage across it decreases as a function of time.

False

An RC circuit is connected across a DC voltage source through an open switch. As soon as the switch is closed, the capacitor charges linearly as a function of time.

False

peak voltage

I0=Irms*sqrt(2) V0=Vrms*sqrt(2)

obtaining I with a function of time

I=(emf/R)e^-t/RC

rms formulas

Irms=.707*I Vrms=.707*V

power

P -measured in watts

electric power formulas

P=IV P=I^2R P=V^2/R

average power formulas

P=IrmsVrms P=Irms^2R P=V^2rms/R

Q and Vc equations with functions of time

Q=C*emf(1-e^-t/RC) Vc=emf(1-e^-t/RC)

resistance formula

R=p(L/A)

Which one of the following is a correct statement for a number of resistors connected in series or parallel? The voltage is different across resistors connected in a parallel circuit. The flow of current is different through resistors connected in a series circuit. The total resistance in a parallel circuit decreases as more resistors are added. The total resistance in a series circuit decreases as more resistors are added. None of the above statements is correct.

The total resistance in a parallel circuit decreases as more resistors are added.

Four unequal resistors connected in series have same current but different voltages

True

to calculate energy

U=P*t

Ohm's law

V=IR

circuits in series formulas

V=V1+V2+V3 V=I(R1+R2+R3) Req=R1+R2+R3 -current equal throughout

When two or more resistors are connected in parallel to a battery, the voltage across each resistor is the same. the equivalent resistance of the combination is less than the resistance of any one of the resistors. the total current flowing from the battery equals the sum of the currents flowing through each resistor. all of the given answers none of the given answers

all of the given answers

consevation of charge

current does not get used up by resistors

emf equation with RC circuits

cursive e=IR + Q/C

As more resistors are added in parallel to a constant voltage source, the power supplied by the source decreases for a time and then starts to increase. increases. does not change. increases for a time and then starts to decrease. decreases.

increases

conductivity

inverse of resistivity 1/p

kirchhoff's first rule

junction rule -sum of all the currents entering a junction must equal the sum of currents leaving the junction

kirchhoff's rules

resistor: same direction as current-negative different direction-positive Battery: negative to positive-positive positive to negative-negative

As a dry cell ages, its internal resistance goes up.

true