Current of Electricity Flashcards
1
Q
What is Electric Current
A
- current is the rate of flow of charge
2
Q
What is electric charge
A
- electric charge Q passing one point in the circuit in an interval of time t is given by Q = It for a constant electric current I in a circuit
3
Q
What is potential difference
A
- potential difference between two points in a circuit is the energy per unit charge transferred from electrical energy to other forms of of energy when charge passes from one point to the other
- V = W/Q
4
Q
What is the electromotive force
A
- electromotive force is the energy transferred per unit charge from other forms of energy into electrical energy when charge is moved round a complete circuit
5
Q
What is resistance
A
- resistance of a conductor is defined as the ratio of the potential difference across it to the current flowing through it
- R = V/I
6
Q
What does Ohm’s Law state
A
- Ohm’s Law states that for a conductor at constant temperature, the current in the conductor is proportional to the potential difference across it
7
Q
What is the resistivity of the material
A
- it is a property of the material and is numerically the resistance of a sample of unit length and unit cross-section area, at a certain temperature
- R = pl/A
8
Q
Power formulas
A
- P = IV — power supplied by source
- P = V2/R
- P = I2R — power dissipated in a device
9
Q
Effects of internal resistance
- E
- VR
- Vr
A
- E = I(R + r)
- VR = IR
- Vr = Ir
10
Q
- output efficiency
- maximum power theorem
A
- R/ (R+r)
- R = r
