Elecricity

Question 1

Forces between charges

Answer 1

Opposite attract
Same repel
Electrostatic force either attractive or repulsive
Gravitational force is always attractive
Electrostatic force is conservative

Question 2

SI units of charge

Answer 2

Coulomb, e=1.60*10^-19 C

Question 3

Coulomb’s law

Answer 3

Magnitude of electrostatic force between two charges separated by distance.

Question 4

Formula for electrostatic force

Answer 4

F=k(q1q2)/r^2
K- coulomb’s constant=8.9910^9 Nm^2/C^2
K=1/(4pi€0)
€0- permittivity of free space=8.8510^-12 c^2/Nm^2

Question 5

Electric field formula

Answer 5

E=F/q0 require presence of test charge

E=k*q/r^2 dn need presence of test charge, but need to know the magnitude of the source chage

Question 6

Stationary test charge

Answer 6

q0

Charge placed in the electric field

Question 7

Stationary source charge

Answer 7

Charge that set up an electric field

Question 8

Direction of electric field

Answer 8

Direction of positive test charge if source charge is presented
If source charge is +, repel away
If source charge is -, accelerate towards

Question 9

Electric field lines

Answer 9

Lines of force
Away from +, end up on - charge
When they are closed to each other, field is stronger. When they are farther apart, field is weaker

Question 10

Total electric field

Answer 10

Every charge will exert its own electric field
Net electric field is a vector sum of all electric fields
E total=E1+E2…..

Question 11

Force on the test charge placed in electric field

Answer 11

F=q0/E
Need to use sign on the charge
If +, F in the same direction with electric field
If -, F in the direction opposite to the field vector.

Question 12

Electric potential energy formula

Answer 12

U=kqQ/r
If charges are like, U +. Less stable situation. U is increasing.
If charges are unlike, U-. More stable situation. U is decreasing.
U=W=Fd= Fr=(kqQ/r^2)*r=kqQ/r
In general, a charge will always move in whatever direction in a crease in the system’s electric potential energy.

Question 13

Electric potential energy definition

Answer 13

Work necessary to move a test charge from infinity to a point in space in a electric field surrounding a source charge.

Question 14

Electric potential

Answer 14

V, volt, 1 J/C, scalar, sign = sign of charge

• ratio of magnitude of charge’s electric potential energy to magnitude of charge
• work that is necessary to move charge from infirmity to a point in electric field to magnitude of charge

Question 15

Electric potential formula

Answer 15

V=W/q, W=kqQ/r
V=kQ/r
For collection of charges V total= V1+V2….

Question 16

Potential difference between two points that are at different distances from the source charge

Answer 16

Vb-Va = Wab/q
Wab - work need to move test charge between a and b
- depends only on potentials at point a and b
- independent of the pathway between a and b

Question 17

Movement of charges in potential difference or voltage

Answer 17

Positive charge moves spontaneously from high voltage to low voltage.
Negative charge moves from low voltage to high voltage.
High potential end in the battery is plus
Low potential end in the buttery is minus

Question 18

Equipotential line

Answer 18

Potential difference between any two points is zero on this line
Concentric circles surrounding source charge
No work is done when move a charge between two points on equipotential line
Work will be done when move from one line to another
Work does not depends on path

Question 19

Electric dipole

Answer 19

Results from two equal and opposite charges being separated a small distance from each other
Can be transient and permanent
V= (kqd/r^2)cos terra
qd - dipole moment p (Cm), vector

Question 20

Direction of dipole moment vector

Answer 20

In physics from negative to positive
In chemistry from positive to negative
Dipole axis goes along distance between dipoles

Question 21

Perpendicular bisector of dipole

Answer 21

Equipotential line that lies between two charges
Angle between it and dipole axis is 90, cos of 90= 0
Electric potential along this line is 0
The magnitude of electric field here E=(1/4pi€0)*(p/r^3)
Electric field vector will be opposite to p

Question 22

Torque about the center of dipole axis

Answer 22

Generated by uniformed electric field where dipole places

=(qd)Esin terra

Question 23

Uniformed electric field

Answer 23

Strength of field is the same everywhere