Current Electricity Flashcards
(14 cards)
Define an electric current.
An electric current I is defined to be the amount of charge per unit time that passes through the cross-section area of a conductor.
Its formula is given by I = Q/t, where Q represents the charge passing through the conductor, and t represents the time taken.
What is the definition of an ampere?
An ampere is defined to be 1 Coloumb per second.
What is conventional current flow, and what is its direction?
The direction of conventional current flow is opposite to the flow of electrons. The conventional current is flowing in the same direction as the positive charges.
Conventional current flows from the positive terminal of a battery to the negative terminal, while electrons flow from the negative terminal of a battery to the positive.
Define the electromotive force of a circuit, and write down its formula.
The electromotive force of an electrical source refers to the work done by the source in driving a unit charge around the closed circuit, where E =W/Q, where W refers to the amount of work done and Q refers to the charge in coulombs.
What is the difference in arrangement of electromotive force/potential difference/voltage in parallel and series circuits?
Given that in this (series/parallel) circuit, there are two cells providing 1V and 2V respectively.
In the circuit where the cells are arranged in a parallel manner, total voltage V = (V1 + V2) (V1V2) = 1.5V
In the circuit where the cells are arranged in a series, total voltage V = V1 + V2 = 3.0V
What is potential difference, and what is its formula?
Potential difference, or voltage is essentially similar to the electromotive force of a closed circuit, and refers to the work done by the electrical source is driving a unit charge through a circuit component. The formula is also the same as that of electromotive force, where V = W/Q, where W refers to work done and Q refers to the charge passing through the closed circuit.
The work done refers to the amount of electrical energy converted to other forms of energy. For example, when a current passes through a bulb in a circuit, the bulb heats up. This highlights how electrical energy is converted to heat energy when the current passes through the bulb.
What is the potential difference across the electrical source/battery in the circuit?
The potential difference across the electrical source would be the voltage of the electrical source. If the voltage of the electrical source is 3V, then the potential difference across the electrical source would be 3V.
What is the definition of resistance and what is the formula for it?
Resistance of a circuit component refers to the ratio of potential difference (V) across the component to the current (I) which is flowing through it.
The formula for calculating resistance is R = V/I
How must the ammeters and voltmeters be connected with circuit components?
Ammeters must be connected in series whitest voltmeters must be connected in parallel.
What is the formula for calculating electrical power?
Electrical power, P = I x V, where I refers to current and V refers to potential difference.
What is the other formula for resistance that is correlated to cross-sectional area?
R = (rho) x (L/A). The resistance of a piece of wire R is related to its cross-sectional area, its resistivity (a fixed property of the wire, and the length of the wire).
Resistance is directly proportional to the length and resistivity of the wire (As length and resistivity increases, so does resistance. ) Yet, it is inversely proportional to the cross-sectional area of the wire. The smaller the cross-sectional area, the greater the resistance.
What is Ohm’s law? What does it state?
The Ohm’s law states that the current flowing through a metallic conductor is directly proportional to the potential difference across it when all other factors such as temperature are constant.
What is the gradient of a I—V Graph?
The gradient of an I—V Graph is the 1/Resistance.
How does temperature affect the resistance of metallic conductors, be it ohmic or non-ohmic?
The resistance of metallic conductors, should they be ohmic or non-ohmic, increases as the temperature increases.
