Physics - Electrostatics Magnetism Flashcards
What does Coulomb’s law quantify?
The magnitude of the electrostatic force between two charges
Coulomb’s law is fundamental in electrostatics, describing how charged objects interact.
What is the formula for Coulomb’s law?
Fe = k * (q1 * q2) / r^2
Here, Fe is the magnitude of the electrostatic force, k is Coulomb’s constant, q1 and q2 are the charges, and r is the distance between charges.
What does ‘k’ represent in Coulomb’s law?
Coulomb’s constant
Coulomb’s constant varies based on the units used in the equation.
What is the value of Coulomb’s constant in SI units?
k = 8.99 × 10^9 N.m²/C²
This value is derived from the permittivity of free space.
What is the permittivity of free space?
8.85 x 10^-12 C²/(N·m²)
This constant is crucial in the calculation of electrostatic forces.
What happens when two unlike charges interact according to Coulomb’s law?
They attract each other
This attraction is a fundamental principle in electrostatics.
What happens when two like charges interact according to Coulomb’s law?
They repel each other
This repulsion is also a fundamental principle in electrostatics.
In which direction does the electrostatic force act?
Along the line connecting the centers of the two charges
The direction of the force is determined by the nature of the charges involved.
Fill in the blank: The electrostatic force Fe is proportional to the product of the magnitudes of the two charges and inversely proportional to the square of the distance between them, expressed as Fe = k * (_______) / r^2.
q1 * q2
This relationship is key to understanding how electrostatic forces operate.
What is an electric field?
A surrounding field created by every electric charge that exerts forces on other charges.
What determines whether the force in an electric field is attractive or repulsive?
The relationship between the stationary test charge q and the stationary source charge Q: opposite charges are attractive, like charges are repulsive.
What are electric fields produced by?
Source charges (Q).
What happens when a test charge (q) is placed in an electric field (E)?
It experiences an electrostatic force (F_e) equal to qE.
How can the magnitude of an electric field be calculated?
Using the equation E = Fe/q = KQ/r^2
Fill in the blank: Electric fields exert forces on other charges that move into the _______.
space of the field.
True or False: Electric fields can only exert attractive forces.
False.
What is the electrostatic force experienced by a test charge in an electric field?
F_e = qE.
What is the relationship between source charges and electric fields?
Source charges produce electric fields.
What is potential energy?
Stored energy that can be used to do something or make something happen.
Name three types of potential energy.
- Gravitational potential energy
- Elastic potential energy
- Chemical potential energy
What is a fourth form of potential energy?
Electric potential energy.
Electric potential energy is dependent on what?
The relative position of one charge with respect to another charge or to a collection of charges.
What is the equation for electric potential energy?
U = kqQ/r
What is electric potential defined as?
The ratio of the magnitude of a charge’s electric potential energy to the magnitude of the charge itself.
How is electric potential expressed mathematically?
V = U/q
What is the unit of electric potential?
Volts (V)
What is the relationship between electric potential energy (U) and electric potential (V)?
U = kqQ/r, where k is a constant and Q is the source charge
V=kQ/r where v doesn’t have two charges
U = qV overall
How can electric potential at a point in space be calculated without a test charge?
By knowing the magnitude of the source charge and the distance from the source charge to the point in space.
What is the equation for electric potential in terms of the source charge?
V = kQ/r
Is electric potential a scalar or vector quantity?
Scalar quantity.
What determines the sign of electric potential?
The sign of the source charge Q.
What is the sign of electric potential for a positive source charge?
Positive.
What is the sign of electric potential for a negative source charge?
Negative.
How is the total electric potential at a point in space calculated for a collection of charges?
It is the scalar sum of the electric potential due to each charge.
What is the equation for force in electrostatics?
Fe = kqQ/r^2
This equation describes the electrostatic force between charges.
What does U represent in the context of electrostatics?
U = kQq/r
U typically represents potential energy in electrostatic contexts.
What does E stand for in electrostatics?
E = kQ/r^2
E represents electric field strength in electrostatics.
What should you memorize for Test Day?
Essential equations and their relationships
Understanding how the equations relate is crucial for problem-solving.
How can you recreate the table related to Coulomb’s law?
Through mathematical manipulation
This involves multiplying by r and dividing by q.
Fill in the blank: To recreate the table from Coulomb’s law, from left to right, you should _______.
multiply by r
Fill in the blank: To recreate the table from Coulomb’s law, from top to bottom, you should _______.
divide by q
True or False: Coulomb’s law can be manipulated mathematically to recreate a table of values.
True
This manipulation aids in understanding the relationships between variables.
What is the high-potential end of a battery called?
The ‘plus’ end
What is the low-potential end of a battery called?
The ‘minus’ end
In terms of electric charge, which direction does positive charge move?
From + to -
In terms of electric charge, which direction does negative charge move?
From - to +
True or False: Positive charge moves from the minus end to the plus end of a battery.
False
Fill in the blank: The definition of current is the movement of positive charge from + to _____.
-
What creates a magnetic field?
Any moving charge
This includes individual charges, mass movement of charge, and permanent magnets.
What is the SI unit for magnetic field strength?
Tesla (T)
1 T = 1 N.s/m.g.
What is the relationship between tesla and gauss?
1 T = 10^4 gauss
The gauss is used for measuring smaller magnetic fields.
How are materials classified based on their magnetic properties?
Diamagnetic, paramagnetic, ferromagnetic
These classifications depend on the presence of unpaired electrons and net magnetic fields.
What defines diamagnetic materials?
Atoms with no unpaired electrons and no net magnetic field
They are weakly repelled by magnets.
List some examples of diamagnetic materials.
- Wood
- Plastics
- Water
- Glass
- Skin
These materials do not stick to magnets.
What characterizes paramagnetic materials?
Atoms have unpaired electrons and can become weakly magnetized in an external magnetic field
They align their magnetic dipoles with the external field.
What happens to the magnetic dipoles of paramagnetic materials when the external magnetic field is removed?
They reorient randomly due to thermal energy
This results in the loss of any net magnetic field.
Provide examples of paramagnetic materials.
- Aluminum
- Copper
- Gold
These materials exhibit weak magnetization in external fields.
What happens when like poles of magnets are brought together?
They repel each other
What creates a magnetic field?
Any moving charge
What configuration of magnetic field lines surrounds a current-carrying wire?
Depends on the shape of the wire
How is the magnetic field produced by an infinitely long and straight current-carrying wire calculated?
What does the variable ‘B’ represent in the equation B = MOI?
The magnetic field at a distance r from the wire
What is the permeability of free space (Mo)?
4 × 10^-7 I.m
What is the relationship between the magnitude of the magnetic field and the distance from the current?
Inverse relationship
What shape do magnetic fields created by straight wires take?
Concentric rings
What is the right-hand rule used for in magnetism?
To determine the direction of the magnetic field vectors
How do you apply the right-hand rule?
Point your thumb in the direction of the current and wrap your fingers around the wire
What is the magnitude of the magnetic field at the center of a circular loop of radius r?
Not provided in the text
What type of charges do magnetic fields exert forces on?
Moving charges
Magnetic fields do not affect stationary charges.
What is the Lorentz force?
The sum of electrostatic and magnetic forces acting on a charge
It accounts for both types of forces a charge experiences.
What is the formula for calculating the magnetic force on a moving charge?
Fb= qvB sin(theta)
Where q is charge, v is velocity, B is magnetic field, and e is the angle between v and B.
In the formula FB = qvB sine(e), what does each variable represent?
- q: charge
- v: magnitude of velocity
- B: magnitude of magnetic field
- e: angle between velocity and magnetic field
Each variable plays a crucial role in determining the magnetic force.
What happens to the magnetic force if the charge is moving parallel or antiparallel to the magnetic field?
It experiences no magnetic force
This occurs because the sine of 0° and 180° equals zero.
What is required for a charge to experience a magnetic force?
A perpendicular component of velocity
The charge must have a component of its motion that is not aligned with the magnetic field.
True or False: Charges can sense their own magnetic fields.
False
Charges only sense the fields created by external charges.
What is the relationship between the angle and the magnetic force in the formula FB = qvB sine(e)?
The magnetic force depends on the sine of the angle
This means that the angle between the velocity and magnetic field affects the force experienced.
What is the value of sin 0°?
0
Sin 0° equals zero, indicating no force on a charge moving parallel to the magnetic field.
What is the value of sin 180°?
0
Sin 180° also equals zero, confirming that no force is experienced by a charge moving antiparallel to the magnetic field.
What does it mean for a charge moving parallel or antiparallel to the magnetic field?
It experiences no force from the magnetic field
This is due to the sine function being zero at these angles.
What is the first step in using the right-hand rule to determine the direction of the magnetic force on a moving charge?
Position your right thumb in the direction of the velocity vector
This establishes the direction of movement.
In the right-hand rule, where do you place your fingers?
In the direction of the magnetic field lines
This represents the orientation of the magnetic field.
What does your palm represent when using the right-hand rule for a positive charge?
The direction of the force vector
This indicates the force acting on a positive charge.
What does the back of your hand represent when using the right-hand rule for a negative charge?
The direction of the force vector
This indicates the force acting on a negative charge.
Fill in the blank: The thumb in the right-hand rule indicates the direction of _______.
velocity
The thumb represents the movement direction like a hitchhiker’s thumb.
Fill in the blank: The fingers in the right-hand rule represent _______.
field lines
Fingers are aligned parallel to the uniform magnetic field lines.
Fill in the blank: The palm in the right-hand rule is used to determine the force on a _______ charge.
positive
This visualizes giving a ‘high five’ to a positive person.
Fill in the blank: The back of the hand indicates the force on a _______ charge.
negative
This visualizes giving a backhand to a negative person.
What is the equation for the magnetic force on a current-carrying wire?
FB = ILB sin(theta)
Where FB is the magnetic force, I is the current, L is the length of the wire in the field, B is the magnitude of the magnetic field, and e is the angle between L and B.
What does the variable ‘I’ represent in the magnetic force equation?
Current
Current is the flow of positive charge.
What does the variable ‘L’ represent in the magnetic force equation?
Length of the wire in the field
L refers to the portion of the wire that is within the magnetic field.
What does the variable ‘B’ represent in the magnetic force equation?
Magnitude of the magnetic field
B indicates the strength of the magnetic field acting on the wire.
What does the angle theta represent in the magnetic force equation?
Angle between L and B
e is the angle formed between the direction of the current and the magnetic field.
True or False: A current-carrying wire does not experience a magnetic force when placed in a magnetic field.
False
A current-carrying wire placed in a magnetic field will experience a magnetic force.
What rule can be used to determine the direction of the magnetic force on a current-carrying wire?
Right-hand rule
The right-hand rule applies to both moving point charges and current-carrying wires.
Fill in the blank: The force created by an external magnetic field on a wire is represented by _______.
FB
FB stands for the magnetic force acting on the wire.
