Electricity and Electrostatics Flashcards
What is the charge on an
electron?
-1
What is the charge on a
proton?
+1
What is the charge on a
neutron?
0
/neutral
Why can electrons move between substances but protons cannot?
Because electrons are much lighter and if a proton moves between a substance then that would change its proton number which would change the element.
How can electrons be transferred?
By friction or by induction.
Why does a charged balloon stick to a neutral wall?
Because the electrons in the wall would be attracted/repelled by the electrons/protons in the balloon.
Define
electric field.
A region where a charged object will experience a force.
How are electrical fields drawn?
By considering it to consist of imaginary lines showing the direction of the force acting on a positive charge.
Where is the force exerted by a charged particle the greatest?
Close to the particle.
What does the density of field lines suggest?
The strength of the forces.
Describe a uniform field.
The strength and direction of the field is the same everywhere. So the lines are parrallel and evenly spaced.
Define
conduction.
The transfer of thermal energy by one particle bumping into another particle and transferring its kinetic energy.
Why is it important that the balloon is an insulator?
So that the electrons the balloon gains/loses stay in one area of the balloon and do not spread out. Resulting in an area of net negative/positive charge compared to the (relatively) neutral rest of the balloon.
What is the earth in physics.
An infinite electron donor/acceptor due to its large mass and electron quantity.
What would happen if you earthed a positively charged object?
The electrons would flow from the earth to the object.
What would happen if you earthed a negatively charged object?
The electrons would flow from the object to the earth.
Why do sparks happen?
A positively charged object will try to grab electrons so that it can become neutral again. Sometimes this pull can be so strong that an electron from a nearby air molecule can be ripped out - leaving behind a positive ion. When this happens, a chain reaction causes lots of molecules to be ionised and a spark forms.
Why do sparks appear in the way that they do?
When a spark happens, electrical potential energy is converted into light, thermal and sound energies.
What is current?
The (rate of) flow of charge.
(/the rate of flow of charged particles)
What is charge measured in?
C, coulombs
What is current measured in?
A, amps
What is time measured in?
s, seconds
What equation links current, charge and time?
(I, Q, t)
current = charge/time
I = Q/t
or Q = It
What direction is electron flow?
negative to positive
What direction is conventional current?
positive to negative
What is an amp?
1 amp is 1 coulomb per second
1A = 1C/s
What is a volt?
1 volt is 1 joule of energy per coulomb of charge
1V = 1J/C
What equation links energy, voltage and charge?
(E, V, Q)
energy = voltage x charge
E = VQ
What equation links energy, voltage, current and time?
(E, V, I, t)
energy = voltage x current x time
E = VIt
evit, ewit, evict / energy from vitamins
Define power
rate of energy transferred
What equation links power, energy and time?
(P, E, t)
power = energy/time
P = E/t
What equation links power, current and voltage?
(P, I, V)
power = current x voltage
P = IV
piv, pov
What is Ohm’s Law?
(V, I, R)
voltage = current x resistance
V = IR
What equation links power, current and resistance?
(P, I, R)
power = current^2 x resistance
P = I^2 R
PIIR, peer
What equation links power, voltage and resistance?
(P, V, R)
power = voltage^2 / resistance
P = (V^2) / R
