Chapter 20: Magnets Flashcards
If the south pole of one bar magnet is brought near the north pole of a second bar magnet, the two magnets will ________
attract
If a bar magnet is divided into two equal pieces, ________
two magnets result
An electric current produces ________
a magnetic field
Which of the following is correct?
1.) When a current carrying wire is in your right hand, thumb in the direction of the magnetic field lines, your fingers point in the direction of the current.
2) When a current carrying wire is in your left hand, thumb in the direction of the magnetic field lines, your fingers point in the direction of the current.
3) When a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
4) When a current carrying wire is in your left hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
When a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current ________
circles the wire in a counter-clockwise direction.
A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, inside the loop? The magnetic field ________
points straight up
For points inside the loop, the magnetic field caused by the current is vertically upwards.
The SI unit of magnetic field is the ________
Tesla
Guass could be used
The direction of the force on a current-carrying wire in a magnetic field is described by which of the following?
perpendicular to both the current and the magnetic field
The force on a current-carrying wire in a magnetic field is the strongest when ________
the current is perpendicular to the field lines
A charged particle moves across a constant magnetic field. The magnetic force on this particle ________
causes the particle to accelerate
Fleming’s left-hand rule:
-Your thumb (representing velocity) points in the direction of the particle’s motion.
-Your index finger (representing the magnetic field) points in the direction of the magnetic field (perpendicular to the velocity).
-Your middle finger (representing the force) will point in the direction of the magnetic force.
A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle’s weight, the particle will ________
follow a circular path
the path of the charged particle moving in a plan perpendicular to a magnetic field is a circle
The magnetic field produced by a long straight current-carrying wire is ________
proportional to the current in the wire and inversely proportional to the distance from the wire
Two long parallel wires carry equal currents. The magnitude of the force between the wires is F. The current in each wire is now doubled. What is the magnitude of the new force between the two wires?
4F
What fundamental fact underlies the operation of essentially all electric motors?
A current-carrying conductor placed perpendicular to a magnetic field will experience a force
A 2.0-m wire carrying a current of 0.60 A is oriented parallel to a uniform magnetic field of 0.50 T. What is the magnitude of the force it experiences?
zero
If current and magnetic field are parallel, the force is zero
A stationary proton is in a uniform magnetic field of 0.20 T. What is the magnitude of the magnetic force on the proton?
zero
An electron moves with a speed of 5.0 x 10^4 m/s perpendicular to a uniform magnetic field of 0.20 T. What is the magnitude of the magnetic force on the electron?
1.6 x 10^-15 N
A solenoid 20 cm long is wound with 5000 turns of wire. What magnetic field is produced at the center of the solenoid when a current of 10 A flows?
0.32 T
A vertical wire carries a current and is in a vertical magnetic field. What is the direction of the force on the wire?
zero, bcz its parallel
A horizontal wire carries a current and is in a vertical magnetic field. What is the direction of the force on the wire?
Out of the page
*Since 𝐹 must be perpendicular to both 𝐼 and 𝐵, you should realize that 𝐹 cannot be in the plane of the page at all.
A positive charge traveling upward enters a uniform magnetic field directed to the right. What is the direction of the magnetic force the charge experiences?
Into the page
C
Cyclotron radius:
radius of the circular path taken by a charge moving through a magnetic field
A 6.0-MeV (kinetic energy) proton enters a 0.20-T field, in a plane perpendicular to the field. What is the radius of its circular path?
B
C
A vertical straight wire carrying an upward 28-A current exerts an attractive force per unit length of 7.8 × 10−4 N/m on a second parallel wire 9.0 cm away. What current (magnitude and direction) flows in the second wire?
F
Which of the solenoids described below has the greatest magnetic field along its axis?
a solenoid of length 2𝐿, with 2𝑁 turns and a current 2𝐼
A 30.0-cm-long solenoid 1.25 cm in diameter is to produce a field of 4.65 mT at its center. How much current should the solenoid carry if it has 935 turns of the wire?
If there is a current in the loop in the direction shown, the loop will:
rotate clockwise
What is the direction of the magnetic field at the center (point P) of the square loop of current?
out of the page
