1 Electrostatics and Current Flashcards
Two insulating materials are rubbed together.
They are charged by friction.
Which particle is transferred between them?
Electrons
Charge does not flow easily through what sort of material?
insulators
eg plastic or wood
What is the current if 7200 C passes in 1 hour ?
I = Q/t
time must be in seconds
1 hour = 1 x 60 x 60 = 3600 secs
I = 7200 C/ 3600 s
I = 2 A
What is the current if 360 C passes a point in a circuit in 2 min?
I = Q/t
time must be in seconds
2 min = 2 x 60 = 120 seconds
I = 360 C / 120s
I = 3 A
Name three uses of electrostatics
- electrostatic smoke removal from chimneys
- photocopier
- inkjet printer
- electrostatic paint sprayer
- electrostatic crop sprayer
Where are neutrons located in an atom?
in the nucleus
If 3nC of electrons were transferred from a cloth to the surface of the rod, what is the charge on the rod?
- 3 nC
negative charge as the rod has gained electrons
What happens when two negatively charge balloons hang side by side?
They repel because
like charges repel
What is the current if 100 C passes in 200s ?
I = Q/t
I = 100 C/ 200 s
I = 0.5 A
What does the prefix ‘nano’ stand for in 10 nC
nano means x 10-9
example 10 nC = 10 x 10-9 C
What is the definition for current?
Current = the rate of flow of charge
I = Q/t
Only electrons are transferred when objects are charged by friction. Why?
Electrons are located in the outer shells of an atom so are easily removed.
But protons are located in the nucleus at the centre of the atom so cannot be removed easily.
If 5 mA flows for 10 minutes, how much charge flows?
Q = I x t
time must be in seconds
t = 10 x 60 = 600 seconds
Current must be in amps
I = 5 mA = 5 x 10-3 A
Q = 5 x 10-3 x 600 = 3C
A negatively charged polythene rod is scraped across a gold leaf electroscope. The gold leaf rises.
Look at the diagram to explain why?
What would you observe if the same thing was done with a postive acetate rod?
The gold foil rises as it is repelled from the central post as like charges repel.
Same would happen for both acetate and polythene but with opposite charges.
What is the symbol for an ammeter and how is it connected in the circuit?
An ammeter is connected in series
A acetate rod is charged by friction? What charge does it gain?
Acetate loses electrons to the cloth to become positively charged
What does the prefix ‘micro’ stand for in 100 uA
micro x 10-6
example : 100 uC = 100 x 10-6 C
What does the prefix milli stand for in 65 mA
milli is x 10-3
example: 65 mC = 65 x 10-3 C
What would happen if two negatively charge balloons were hung side by side?
They would repel because
like charges repel
If 100 A flows for 10 s, how much charge passes?
Q= I x t
Q = 100 A x 10 s = 1000 C
What is the current if 10 nC passes in 5 s ?
I = Q/t
first convert 10nC to coulombs
10nC = 10 x 10-9 C
I = 10 x 10-9/ 5
I = 2 x 10-9 A
What equation links charge, current and time?
Charge = current x time
Q=It
or
Current = charge / time
I=Q/t
What would happen if two negatively charge balloons were hung side by side?
The would repel because
like charges repel
Where are protons located in an atom?
the nucleus
What sort of material will allow charge to flow through it?
conductors such as a metal
What is the relative charge of an electron?
-1
What charge would a rod adopt if 5nC of electrons were transferred from its surface to a cloth?
+ 5 nC
What would happen if two positively charge balloons were hung side by side?
The would repel because like charges repel
How can a charged object be discharged?
Earth it. Connect a wire conductor from the object to a stake in the ground.
What is the relative charge of a proton?
+1
A polythene rod is rubbed with a cloth. What happens?
Electrons transfer from the cloth to the rod.
The polythene rod becomes negatively charged
The cloth becomes postively charged
What is the relative charge of neutron?
0
An acetate rod is rubbed with a cloth. What happens?
Electrons transfer from the rod to the cloth.
The acetate rod becomes positively charged
The cloth becomes negatively charged
If 4 A flows for 2 minutes, how much charge flows?
Q = I x t
Q = 4 A x (2 x 60s ) = 480C
time must always be converted into seconds
Where are electrons located in an atom?
shells orbiting the nucleus
Name three dangers of electrostatic charge
- Refueling cars or aircraft
- explosion of dust or fine powder in industry
- Lightning from charge build up in clouds
- Spark in operating theatre- explosion of oxygen
What can we use to measure charge?
A nanocoulombmeter
How can we reduce the electrostatic force acting on the objects below?
Move the objects further apart OR decrease their charge.
What would happen if a negatively charged balloon and a positively charge balloon were hung side by side?
They attract because
unlike charges repel
