Chapter 8 - Charge And Current Flashcards
What is electrical charge ? How do the charges interact ?
Electric charge is a physical property that all bodies possess and there are two different types of charge:
● Positive (+) charge
● negative (-) charge
Charges interact via the electrostatic force and depending on the types of charges, there are two possibilities:
● two of the same charge will repel
● two opposite charges will attract
What is a coulomb ?
The coulomb (C) is the base unit of electric charge.
One coulomb (1C) of charge is defined as the amount of charge that passes a point per second when there is a current of one amp (1 A).
What’s the charge on a electron and proton ?
-1.6 x 10-19 Electron
+1.6 x 10-19. Proton
What is elementary charge ?
All charges are found to be a multiple of the elementary (fundamental) charge
How much is one elementary charge in Coulombs ? 1e = ?C
1e = 1.6 x 10*-19 C
What is electrical current ?
Electric current is the rate of flow of electric charge
What is the equation for Electric current ?
I = Q / t
Q = charge which is measured in Coulombs (C)
I = current which is measured in Amps (A)
t = time which is measured in seconds (s)
What is net charge ?
How does an object become charged ?
How can net charge be expressed as a multiple of e ?
It is the overall charge on an object for example an object can be positively charged because its lost electrons.
The charge on most objects results from either a gain or loss of electrons by the object
Q = +- n e
Charge = plus or minus , random number , e
What’s a conventional current ?
Conventional current or simply current, behaves as if the positive charge carriers cause current flow.
Conventional current flows from positive to negative terminals
However in real life this is not how current actually flows. Electrons cause the current to flow and electrons flow from neg to pos terminals. Therefore conventional current is just a concept
What is the flow of electrons termed as ?
Electron current ( electrons flow from neg to pos terminals )
Why do electrons flow from neg to pos terminals and why do electrons cause current flow ?
This is because inside the metal wire there is metallic bonding and this is where the positive metal ions form a regular lattice structure and have delocalised electrons flowing around them. So the delocalised electrons get repelled from the -ve terminal and are attracted to the +ve terminal.
How do Ammeters work and what do they do ?
Ammeters measure the rate of flow of current
In order to measure the current, the charge (or part of it ) must pass through the ammeter itself
How must you place an Ammeter, to make it not effect the resistance ?
To make the ammeter not effect the resistance, it must be placed in series and have a negligible charge
What happens when you turn the dial on a digital ammeter ?
When you turn the dial on a digital ammeter, you alter the fraction of current passing though the ammeter, the remainder of the current passes through a bypass
In any closed system, the total charge in the system is …
Conserved ( stays the same ) because a closed system means no energy can get out of the system and no energy can go into the system
