35 terms

Electric Forces and Electric Fields

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How do objects become charged?
By gaining/losing electrons
Electric charge is always _______.
Conserved
____________ is quantized.
Electric charge
What is the unit of one charge?
1 e
What is the numerical value of one charge?
1 e = 1.6 x 10^-19 Coulombs
Quark charge =
e/3
The SI unit of a charge is in ______.
Coulombs
Materials where an electric charge moves freely throughout are known as ___________.
Conductors
Materials where a charge does not move freely throughout are known as __________.
Insulators
What happens when an insulator is charged?
Only the small spot which was directly contacted with a charge remains charged
What is the name of materials that contain properties somewhere between conductors and insulators?
Semiconductors
What are two examples of semiconductors?
Silicon and Germanium
What sign does an object being charged by conduction have?
The same sign as the object doing the charging
Describe the process of conduction:
1. A negative rod repels a sphere's electrons, leaving that side of the sphere with a local positive charge.
2. After contact between the two, the electrons from the rod flow to the sphere to neutralize the local positive charge.
3. When the rod is removed, a negative charge remains on the sphere.
Describe the process of charging by induction:
1. A neutral sphere has an equal number of positive and negative charges
2. Electrons redistribute when a charged rod is brought close
3. Some electrons leave the grounded sphere through ground wire and there is an excess pos charge
4. the remaining electrons distribute themselves uniformly and there is a net positive charge on the sphere's surface.
What is a grounded object?
An object connected to a conducting wire or copper pipe buried into the earth.
Does charging an object by induction require contact?
No
Does charging an object by conduction require contact?
Yes
Does the inducing object lose any of its charge in conduction?
Yes
Does the inducing object lose any of its charge during induction?
No
What is the charge on an object charged by induction?
Opposite that of the inducing object
Which is stronger for any two given objects/particles: gravitational or electric force?
electric force
Conversion for 1 nm =
10^-9 m
The electric field around a positive charge is:
radially outward
_____________ exerts a force on any other charged object within range.
Electric field
What is a "test charge"?
A small charge (usu. positive) used to obtain the electric force at a given location.
Describe the electric field around a simple negative charge:
Radially inward
A dipole consists of:
two equal and opposite charged
In what direction to field lines go?
From positive to negative charges ALWAYS
Do field lines cross each other?
No
What indicated field strength?
The density of field lines
When does the electric field always have the same direction as the electric force on a test charge?
When the test charge is positive
What do few field lines between charges indicate?
A weak field
E is large when field lines are _______ and small when field lines are _______
close together
far apart
Electric forces can produce ________
acceleration