(1) When looking at the circuit diagram of the physical diagram, the key is to look at the drawings. If you can't understand painting, you can't draw well. There is an internal rule in the senior high school entrance examination that there is no need to mix drawings. Then you should know in your heart that there are actually only two kinds of circuits in the physical diagram, one is series and the other is parallel. Series circuits are easy to identify. First find the positive pole of the power supply, and use the pencil tip to advance in turn along the current direction until the negative pole of the power supply. Determine the position of each component, and then draw. The order is: draw the battery pack first, according to the standard arrangement order of components, horizontally and vertically, and there can be no components in the corner. If there is a voltmeter, it is necessary to accurately determine which section of the measuring circuit it is in, and put the voltmeter at both ends of the circuit under test under the condition that the circuit is correct. For the parallel circuit, the judgment method is as follows: from the positive pole of the power supply, find the bifurcation point along the current direction and mark it with the word "fen". (Ignore the voltmeter when disconnecting, and don't handle it when disconnecting) Use two pencils to advance along the current direction from the bifurcation point until the two pen tips meet, and this point is the intersection point. And marked with the Chinese word "He". First of all, we need to know how many branches there are, how many components are there in each branch, and what are they? Pay special attention to the main road between the distribution point and the positive pole of the power supply, and the main road between the distribution point and the negative pole of the power supply. See which components are on the main road, and start to make the circuit diagram on the basis of all clarity. The specific steps are as follows: first draw the battery pack, draw two main roads respectively, and draw everything in the main road. Draw branches between the branch point and the junction point respectively, draw several branches (in most cases, there are only two branches), and accurately draw the component specifications in each branch in order, and the drawing requires horizontal and vertical. After checking the pencil drawing, draw the voltmeter to both ends of the circuit under test.
(2) Look at the circuit diagram and draw the components.
Methods: Look at the circuit first: mixed connection is not allowed, there are only two kinds: series connection and parallel connection. Series connection is easy to identify, and parallel connection is the key. If it is a parallel circuit, find out the dividing point and combining point on the longer circuit and mark it. And the location of each component is clearly defined. (first find out whether there is an open shunt and ammeter on the main road. ) Connect the physical diagram, first connect the battery pack, find the positive pole of the power supply, start from the positive pole, connect the main circuit components, and then connect the branches after finding the branch points. Never scribble in order. Until the junction, draw another one [note that the wires must not cross, and the wires must be pulled to the terminal (switch, ammeter, voltmeter, etc.). ) to connect the ammeter, and the voltmeter should pay attention to the positive and negative poles. When encountering a sliding rheostat, pull it up and down. After checking that the circuit is correct, finally connect the voltmeter to both ends of the circuit under test.
(3) The circuit design method is as follows:
First, read the questions, examine the questions, and sort out the circuits. There are generally only two kinds of circuits, series and parallel. It is easier to connect in series. The key is to pay attention to all circuits in which the main switch and ammeter are connected in parallel. The ammeter and switch in the branch only care about the electrical appliances in this branch, and then draw a picture in the branch. Finally, put the voltmeter at both ends of the electrical appliance under test. After checking the circuit, the circuit must be drawn with a pencil, horizontally and vertically, and components are not allowed to be drawn at corners, and the drawing should be standardized.
(4) Identify the wrong circuit. General errors occur in the following situations:
1, whether there is a power short circuit, that is, the current directly returns to the negative pole of the power supply without going through the electrical appliance;
2, whether there is a local short circuit, local short circuit electrical appliances can't work;
3. Whether the voltmeter, ammeter and positive and negative terminals are connected incorrectly, or the range is improperly selected (too large or too small);
4. The sliding rheostat is wrongly connected (all up or all down).