8TH GRADE · ELECTRIC CURRENT
Current, voltage and devices
Ammeter, voltmeter and safe switching on of devices.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Electric current
A physical quantity equal to the charge passing through the cross section of a conductor per unit time.
The ammeter is connected in series so that the same current passes through it as through the element under study.
Electrical voltage
A physical quantity equal to the work done by an electric field to transfer a unit charge.
The voltmeter is connected in parallel to the section, since it compares the electrical states of its two points.
Connecting measuring instruments
The ammeter is connected to the open circuit, and the voltmeter is connected to the ends of the selected section, taking into account the polarity.
Do not connect the ammeter directly to the source: its low resistance will create a dangerously high current.
Physical quantities
Electric current
Electric charge passing through a section per unit time.
Unit: ampere ·
Voltage
Field work on the transfer of a unit electric charge.
Unit: volt ·
Electric field work
The work of the electric field when a charge is transferred across an area.
Unit: joule ·
Lesson formulas
Electrical voltage
The voltage is equal to the work done by the electric field divided by the transferred charge.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.