Electricity Flashcards
Current in a wire consist of a flow of …
electrons from negative to positive
Conventional current is drawn from …
Positive to negative
Current is defined as
The rate of flow of charge
Current in an electrolyte solution is a flow of
Ions
Charge has a unit of the
Coulomb
The coulomb is defined as
One coulomb of electric charge passes a point in one second when there is an electric current of one ampere
What is the charge of an electron?
1.6*10^-19
What is Kirchhoff’s first law?
At any point in an electrical circuit the sum of the currents into that point is equal to the sum of the currents out of the point, electrical charge is conserved
Current in a series circuit is
The same at all points
What is the definition of p.d.?
The energy transferred from electrical energy to other forms per unit charge
What is electromotive force?
The energy transferred from chemical energy to electrical energy per unit charge
What is the definition of the volt?
The pd across the component when one joule of energy is transferred per 1 coulomb passing through the component
What is the definition of resistance?
The ratio of the pd across the component to the current in the component (R=v/I)
What is the definition of the ohm?
The resistance of a component that has a pd of one volt per unit ampere
What is resistance?
The ratio of the p.d. across the component to the current in the component
In a series circuit the supply p.d. is …
equal to the sum of the p.d.s across the individual components in the circuit
What is the definition of the ohm?
The ohm is the resistance of a component that has a p.d. of 1 volt per unit ampere
In a parallel circuit the pd …
across every parallel branch is equal
What is Ohm’s law?
The potential difference across a conductor is directly proportional to the current in the component as long as its temperature remains constant
Equation linking resistivity, cross sectional area and length
P=r x a/l
What are the three equations used to calculate power?
P=iv
P=i^2R
P=v^2/R
What is the definition of power?
The rate at which energy is transferred
The kilowatt hour is an alternative unit for…
Energy
What the definition of the kilowatt hour?
The energy transferred by a 1kw device in a time of an hour
1kwh=
3.6 MJ
Kirchoffs 2nd law states:
The sum of the emfs round a loop in a circuit is equal to the sum of the pd in the same loop
Internal resistance is defined as
The resistance of a source of emf due to its construction
Terminal pd is defined as
The pd across a source
Lost volts are
The pd across the internal resistance of a source of emf
Equation linking lost volts, emf and terminal pd
Emf= lost volts + terminal pd
What is the potential divider equation
Vout = vin x R2/R1+R2
