1. Simple circuit
1.Circuit
Circuit refers to the path through which current flows.The simplest circuit consists of power supply, electrical appliances (also called load), controlswitch, The wire consists of four parts.
2.Circuit diagram
A circuit can be represented by physical objects, but if each circuit is drawn in physical objects, it is troublesome and inconvenient. For convenience, circuits are often drawn in the form of circuit diagrams.
A circuit diagram refers to a diagram drawn with simple conformance to the actual objects in the circuit.
two.Series-parallel circuit
1.Series circuit
Connecting two or more electrical appliances first in sequence with no branches in the middle is called a series circuit.
2.Parallel circuit
Connecting one end of several electrical appliances together and the other end is also called a parallel circuit.
3.Hybrid circuit
The electrical appliances in a circuit are connected in series and in parallel, which is called a hybrid circuit.
4.The characteristics of series and parallel
If the electrical appliances are pureresistanceSexual, the existing electrical appliances do not contain coils,capacitanceWait.
(1) Series features
A. The total resistance is equal to the sum of the sub-resistances. That is: R=R1+R2+……+Rn.
B. The total current is equal to the current flowing through each resistor. That is: I=I1+I2+……+In.
C. The total voltage is equal to the sum of the voltages across the resistors. That is: U=U1+U2+……+Un.
(2) Parallel characteristics
A. The reciprocal of the total resistance is equal to the sum of the reciprocal of the sub-resistances. That is: 1/R=1/R1+1/R2+……+1/Rn.
B. The total current is equal to the sum of the currents of the branches. That is: I=I1+I2+……+In.
C. The tota
1. Simple circuit
1.Circuit
Circuit refers to the path through which current flows.The simplest circuit consists of power supply, electrical appliances (also called load), controlswitch, The wire consists of four parts.
2.Circuit diagram
A circuit can be represented by physical objects, but if each circuit is drawn in physical objects, it is troublesome and inconvenient. For convenience, circuits are often drawn in the form of circuit diagrams.
A circuit diagram refers to a diagram drawn with simple conformance to the actual objects in the circuit.
two.Series-parallel circuit
1.Series circuit
Connecting two or more electrical appliances first in sequence with no branches in the middle is called a series circuit.
2.Parallel circuit
Connecting one end of several electrical appliances together and the other end is also called a parallel circuit.
3.Hybrid circuit
The electrical appliances in a circuit are connected in series and in parallel, which is called a hybrid circuit.
4.The characteristics of series and parallel
If the electrical appliances are pureresistanceSexual, the existing electrical appliances do not contain coils,capacitanceWait.
(1) Series features
A. The total resistance is equal to the sum of the sub-resistances. That is: R=R1+R2+……+Rn.
B. The total current is equal to the current flowing through each resistor. That is: I=I1+I2+……+In.
C. The total voltage is equal to the sum of the voltages across the resistors. That is: U=U1+U2+……+Un.
(2) Parallel characteristics
A. The reciprocal of the total resistance is equal to the sum of the reciprocal of the sub-resistances. That is: 1/R=1/R1+1/R2+……+1/Rn.
B. The total current is equal to the sum of the currents of the branches. That is: I=I1+I2+……+In.
C. The total voltage is equal to the voltage of each branch. That is: U=U1+U2+ …… +Un.
three.Voltage
1.What is voltage
2. The work done by the electric field force to move a unit of positive charge from one point to another is called the voltage between these two points, denoted by U. Voltage classification Voltage is divided into DC voltage and AC voltage.
The voltage whose magnitude and direction do not change with time is called DC voltage.
The voltage whose magnitude and direction change periodically with time is called AC voltage.
3.Voltage measurement
Voltage measurement voltmeter. When measuring, pay attention to the voltmeter and connect it to both ends of the electrical appliance under test. If it is a DC voltage, also pay attention to the polarity, that is, the "+" pole of the voltmeter is connected to the high potential of the electrical appliance under test; the "one" of the voltmeter The pole is connected to the low potential of the electrical appliance under test.
Four.Current
1.What is current
The directional movement of the charge forms an electric current.
2.Classification of current
The current is divided into DC and AC.
The current whose magnitude and direction do not change with time is called direct current.
The current whose magnitude and direction change periodically with time is called alternating current.
3. Current measurement:
An ammeter is used for current measurement. When measuring, pay attention to connect the ammeter in series with the circuit of the electrical appliance under test, and pay attention to the polarity if it is a direct current. which is:
The "+" pole of the ammeter corresponds to the positive pole of the power supply. The "-" pole of the ammeter corresponds to the negative pole of the power supply.
five. resistance:
1. What is resistance:
Resistance refers to the obstructive effect of an object on the current.
4. Classification of resistance:
The resistors include fixed resistors, variable resistors, thermistors, photoresistors, varistors and so on.
5. Resistance measurement:
The resistance can be measured with an ohmmeter (or the ohmmeter of a multimeter). Pay attention to the measurement in the open circuit state, can not measure a certain resistance in the circuit, especially can not measure the resistance when the resistance is charged.
six. Ohm's Law:
Ohm's law is divided into partial-circuit Ohm's law and full-circuit Ohm's law.
1. Ohm's law of partial circuits: In partial circuits that do not contain a power source, the current I flowing through the conductor is proportional to the point voltage U at both ends of the conductor. It is inversely proportional to the resistance R of this section of conductor. This law is called Ohm's law of partial circuits. Its mathematical expression is: I=U/R.
2. Ohm's law of the whole circuit: In a closed circuit with a power supply, the current intensity I in the circuit is proportional to the electromotive force E of the power supply and inversely proportional to the resistance of the entire circuit. This law is called Ohm's law of the whole circuit. Its mathematical expression is: I=E/(R+r)
The current whose magnitude and direction do not change with time is called direct current.
The current whose magnitude and direction change periodically with time is called alternating current.
