test 2: DC circuits & capacitors + magnetic fields & forces mcq questions

two resistors,

[R1= 2.0Ω, R2= 3.0Ω, R3=6.0Ω] connected in series across a 22V battery

what is the current in the circuit?

A) 1.0A

B) 2.0A

C) 2.2A

D) 3.7A

E) 11A

series sum for resistors

solve for current I through ohm’s law, V=IR → I=V/R_eq

B) 2.0A

ohm’s law

V=IR

how do you find C_eq for parallel capacitors?

P.S. → C_eq for parallel capacitance is parallel sum !!

C_eq=C₁ + C₂ + C₃…

how do you find C_eq for series capacitors?

| = | + | + |…

1/C_eq = 1/C₁ + 1/C₂ + 1/C₃

how do you find R_eq for series resistors?

series sum,

R_eq=R₁ + R₂ + R₃

how do you find R_eq for parallel resistors?

| = | + | + |…

1/R_eq = 1/R₁ + 1/R₂ + 1/R₃…

three resistors,

[R₁=6.0Ω, R₂=6.0Ω, R₃=3.0Ω] connected in parallel

what is the equivalent resistance?

A) 1.2Ω

B) 1.5Ω

C) 2.0Ω

D) 3.0Ω

E) 15Ω

resistors in parallel → | = | + | + |…

B) 1.5Ω

terminal voltage

ΔV = ϵ − Ir

a battery has an emf of 12.0V and an internal resistance of 0.50Ω. it supplies a current of 3.0A to an external circuit. the terminal voltage is…

A) 10.5V

B) 11.0V

C) 12.0V

D) 13.5V

E) 15.0V

terminal voltage, ΔV = ϵ − Ir

A) 10.5V

time constant, τ, of a circuit

τ = RC

the time constant of an RC circuit is increased by…

A) decreasing both R and C

B) increasing only the resistance

C) decreasing only the capacitance

D) decreasing the resistance

E) decreasing both R and increasing C

time constant, τ = RC, says R and C are proportional so increasing R will increase C

B) increasing only the resistance

immediately after an initially uncharged capacitors begins charging…

A) the capacitor acts like an open circuit

B) the current in zero

C) the current is maximum

D) the capacitor voltage equals the battery voltage

E) the resistor has zero voltage drop

when a capacitor is uncharged, it’s voltage is zero. at the very start of charging it acts like a short circuit. the maximum possible current flows through the resistor so the current is at its maximum for that moment

C) the current is maximum

a proton (+) moves east while the magnetic field points upward. the magnetic force is directed…

A) north

B) sourth

C) east

D) west

E) zero

B) south

magnetic force

F=qvBsinθ

an e^- enters a uniform magnetic field with its velocity parallel to the magnetic field. the magnetic force on the electron is…

A) macimum

B) zero

C) toward the field

D) opposite the field

E) depends on the speed

magnetic force, F=qvBsinθ

→ when velocity is parallel to the field, the angle θ=0, so the magnetic force becomes 0

B) zero

magnetic field (produced by a long, straight wire)

B=(μ_o​I)/(2πr)

a straight wire carries a current of 8.0A. the magnetic field 5.0cm from the wire is closest to…

A) 1.6×10^-5T

B) 3.2×10^-5T

C) 6.4×10^-5T

D) 1.0×10^-4T

E) 3.2×10^-4T

magnetic field (produced by a long, straight wire), B=(μ_o​I)/(2πr)

B) 3.2×10^-5T

electromagnetism says current flowing in the same direction do what to wires?

attract each other

electromagnetism says current flowing in the opposite direction do what to wires?

push wires apart

two long parallel wires carry currents in the same direction. the wires…

A) repel

B) attract

C) exert no force

D) rotate

E) become magnetized

current flowing in the same direction attract the wires together

B) attract

a proton moves perpendicular to a uniform magnetic field. which quantity remains constant?

A) velocity

B) acceleration

C) direction of motion

D) speed

E) magnetic force

the magnetic force is ALWAYS perpendicular to velocity, so it does no work

→ meaning the particle’s speed and kinetic energy remain constant

D) speed