Electrical Circuits and DC Electricity Flashcards
Describe the motion of the electrons in a DC circuit.
They drift towards the positive end of the cell, colliding with vibrating atoms in the wire as they do so.
Define the internal resistance of a cell.
E = V + Ir, Where E is the emf, V is the potential difference across the load on the cell, I is the current produced by the cell and r is the internal resistance.
State one similarity and one difference between e.m.f. and p.d..
They have the same unit.
For e.m.f. energy is transformed from other forms to electrical. For p.d. energy is transformed from electrical to other forms.
What is potential difference?
The energy transferred from electrical energy to other forms (light, heat, etc.) per unit charge.
What is current?
The rate of flow of positive charge.
What is resistance?
The opposition to the flow of current. The voltage per unit current.
What is resistivity?
The resistance between the ends of a 1m length of material which has a cross-sectional area of 1m^2
What is mean drift velocity?
The average displacement travelled by an electron through a circuit, per unit time.
What is emf?
The energy transferred from chemical and other forms to electrical energy per unit charge.
What is 1 Coulomb?
The amount of charge flowing in 1 second when a current of 1A flows.
What is 1 Volt?
The potential difference across a 1 ohm resistor, which causes a current of 1A to flow.
What is 1 Ohm?
The resistance of a resistor with a potential difference of 1V across it and a current of 1A flowing through it.
What is Ohm’s Law?
For a metallic conductor at constant temperature, the current through it is directly proportional to the
potential difference across its ends.
What is 1 Amp?
The current flowing through a resistor of 1 ohm with a potential difference of 1V across it.
What is Kirchoff’s First Law?
Based on conservation of charge, at any point in a circuit, the total current into the point is equal to the total
current out of the point.
