Physics Test 2
A 100-W resistance heater is connected to a 110-V dc source. What current flows through the heater?
.91 A P=IV
A proton moving eastward with a velocity of 5.0 km/s enters a magnetic field of 0.20 T pointing northward. What are the magnitude and direction of the force that the magnetic field exerts on the proton? (e = 1.60 × 10-19 C)
1.6 × 10-16 N upwards Magnetic force = q ( v x B)
A battery has an emf ε = 78.0 V and an internal resistance r = 4.0 Ω, as shown in the figure. A current of 4.7 A is drawn from the battery when a resistor R is connected across the terminals a and b. The power dissipated by the resistor R is closest to
300 W.
A long wire carrying a 2.0-A current is placed along the y-axis. What is the magnitude of the magnetic field at a point that is 0.60 m from the origin along the x-axis? (μ0 = 4π × 10-7 T ∙ m/A)
B=uI/2pir .67
A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to balance the weight of the rod?
F=ILB and F=mg = ILB=mg 4.9 A
A certain metal wire has a cross-sectional area of 1.0 cm2 and a resistivity of 1.7 × 10-8 Ω ∙ m. How long would it have to be to have a resistance of 1.0 Ω?
R=Pl/A cm^2-> m X 10^-4 divide 1000 =5.9m
Copper wire #1 has a length L and a radius b. Copper wire #2 has a length 2L and a radius 2b. Which statement about the resistance across the ends of the wires is true?
The resistance of wire #1 is twice as high as that of wire #2. R=K(L/b^2)
T or False: The figure shows electrons passing through a resistor. Point b is the side of high potential and point a is the side of low potential.
True
What is the voltage drop across a 5.0-Ω resistor if the current through it is 5.0 A?
V=IR I=25
When the switch is closed in the circuit shown in the figure, the wire between the poles of the horseshoe magnet deflects upward. From this you can conclude that the left end of the magnet is
a south magnetic pole
If you were to cut a small permanent bar magnet in half,
each piece would in itself be a smaller bar magnet with both north and south poles.
A positive charge is moving to the right and experiences an upward magnetic force, as shown in the figure. In which direction must the magnetic field have a component?
into the page thumb is showing the force
An ideal ammeter should
introduce a very small series resistance into the circuit whose current is to be measured.
An electron is moving to the right, as shown in the figure. Suddenly it encounters uniform magnetic field pointing out of the page. Which one of the three paths shown will it follow in the field?
path a
The direction of the force on a current-carrying wire in a magnetic field is
perpendicular to both the current and the magnetic field.
If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will
quadruple in magnitude. P=I^2R
A galvanometer can be converted to an ammeter by the addition of a
small resistance in parallel
When unequal resistors are connected in series across an ideal battery,
the current flowing in each is the same.
Kirchhoff's junction rule is a statement of
the law of conservation of charge.
Kirchhoff's loop rule is a statement of
the law of conservation of energy.
When unequal resistors are connected in parallel in a circuit,
the potential drop is always the same across each resistor. Ieq=I1+I2+I3
A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current?
thumb shows force index shows current *Upward