10TH GRADE · DIRECT CURRENT
Current work and electrical circuits
Work, power, heat, electrolysis and resistor connections.
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Basic Concepts
Joule-Lenz law
The law of heat release by electric current in a conductor.
Electrical energy is converted into internal energy: with constant current, heat grows especially quickly with increasing current.
Electrolysis
The release of a substance on the electrodes when current passes through the electrolyte.
The amount of released substance is determined by the passed charge q = It and the electrochemical equivalent of the substance.
Series connection of resistors
A connection of resistors without branching, in which the same current passes through them.
The current through the elements is the same, the voltages add up, and the total resistance is equal to the sum of the resistances.
Parallel connection of resistors
A connection of resistors between two common nodes such that they have the same voltage.
The voltage of the branches is the same, the total current is divided between them, and the equivalent resistance is less than the smallest of the branches.
Physical quantities
Electric current power
Electrical energy transferred per unit of time.
Unit: watt ·
Heat of current
Energy released by current in the form of heat.
Unit: joule ·
Current source efficiency
The fraction of source power transferred to the external circuit.
Unit: dimensionless quantity
Electrochemical equivalent
The mass of a substance released by a charge of one coulomb.
Unit: kilogram per pendant ·
Temperature coefficient of resistance
Relative change in resistance when heated by one degree.
Unit: reverse kelvin ·
Resistance at zero temperature
The reference resistance of a conductor at zero degrees Celsius.
Unit: ohm ·
Number of identical resistors
The number of identical resistors in the connection.
Unit: dimensionless quantity
Lesson formulas
Work of electric current
The work done by current can be expressed in terms of charge, current, voltage, resistance, power and time.
Equivalent Energy Units
A joule is equal to a watt-second and a volt-coulomb.
Electric current power
Power can be calculated by current, voltage, resistance or work.
Watt through Volts and Amperes
One watt is equal to one volt-ampere.
Joule-Lenz law
The heat of the current is proportional to the square of the current, resistance and time.
Current source efficiency
The efficiency of the source is equal to the proportion of the total resistance attributable to the external circuit.
Faraday's law for electrolysis
The mass of the released substance is proportional to the charge passing through the electrolyte.
Dependence of resistance on temperature
The resistance of a metal increases approximately linearly with temperature.
Series connection of resistors
In a series connection, the current is the same, resistance and voltage are added.
Identical resistors in series
The total resistance of identical series resistors is equal to the resistance of one multiplied by the number of resistors.
Parallel connection of resistors
In a parallel connection, the currents add up, the voltage is the same, and the conductivities add up.
Two resistors in parallel
The equivalent resistance of two parallel resistors is equal to the product divided by the sum.
Identical resistors in parallel
The total resistance of identical parallel resistors is equal to the resistance of one divided by their number.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.