How is the second year of junior high school physics series and parallel taught?

If you are more relaxed in class, the students will not be nervous, so that the cooperation between teachers and students will be better.

What does a teacher listen to? Now you are sharpening your gun, this is the first problem you solve Isn't the teacher just looking at the student's reaction, to make the students lie there, listless, no matter how good you speak, the teachers will judge you to fail You are a newcomer, if you are invincible, how can those experienced teachers mix?

Take it easy, just talk about it, young people, allow those who make mistakes, and then correct them for the better Don't have too much pressure

1． i=i1=i2=…=in (characteristic of the current in a series circuit: the currents are equal everywhere).

2． u=u1+u2+…+un (characteristic of voltage in series circuits: in series circuits, the total voltage is equal to the sum of the voltages at both ends of each part of the circuit).

3． r=r1+r2+…+rn (characteristic of resistance in series circuits: the total resistance is equal to the sum of the resistances of the parts of the circuit).

1.The series partial pressure is not split.

Parallel shunt does not divide pressure.

The total resistance of the series circuit is the sum of the resistors.

The reciprocal of the total resistance of the parallel circuit is the sum of the reciprocals of each resistor 2There is only one path in the series circuit, and as long as one place is disconnected, the entire circuit is not connected. And each parallel element in the parallel circuit forms a path, and one path is disconnected, which does not affect the energization of other paths3

The current circuit that connects electrical appliances, power supplies, switches, and wires is called a circuit. In parallel circuits, the voltages are equal everywhere, and each sub-voltage is equal to the power supply voltage, that is, the total voltage; The sum of the current is equal to the total current, and the magnitude of the current is related to the resistance, the greater the resistance, the smaller the current. In series circuits, the currents are equal everywhere, and each subcurrent is equal to the total current; And the sum of the subvoltages is equal to the total voltage.

The current flow method is usually used to determine the connection of a circuit. If the current passes through each consumer in sequence without shunting, the consumer is connected in series; If the current through the consumer is bifurcated, i.e., the current passing through each consumer is part of the total current, then the electricity is connected in parallel. When judging the connection of a circuit, it is usually possible to use a wire to connect two points of the circuit, and in the junior high school stage, the resistance of the wire can be ignored, so it is possible to see the two points connected by a wire as a point, so sometimes it is convenient to use the "node" method to judge the connection of the circuit.

The series connection of resistors has the following characteristics: (refers to R1, R2 series series, the more strings, the greater the resistance) Current: i=i1=i2 (the current is equal everywhere in the series circuit) Voltage: u=u1

u2 (the total voltage is equal to the sum of the voltages everywhere).

Resistance: r=r1

r2 (total resistance is equal to the sum of each resistance) If n equal resistors are connected in series, then there is r total = nr voltage divider: =; Calculate u1, u2, available:;

Proportional relationship: current: i1:i2=1:1

The parallel connection of resistors has the following characteristics: (refers to R1, R2 in parallel, and the more they are combined, the smaller the resistance) Current: i=i1

i2 (the trunk current is equal to the sum of the currents of each branch).

Voltage: U=U1=U2 (Trunk voltage is equal to the voltage of each branch) Resistance: (The reciprocal of the total resistance is equal to the reciprocal sum of each resistor) If n equivalent resistors are connected in parallel, then there is r total = r

Diversion effect:; Compute i1, i2 is available.