Answer
According to Ohm's law, the current in a closed circuit is equal to the algebraic sum of the emf acting in the circuit divided by the total resistance of the circuit.
The algebraic sum of the EMF is E=12V-10V+2V=4V
The total resistance of the circuit is R=r1+r2+r3+R1234+R56
R1234 consists of two parallel-connected chains of two series-connected resistances (R1, R2 and R3, R4, respectively)
The total resistance of the circuit is 4+1+4+7.2+1=17.2 Ohm
Ammeter A" shows the total current in the circuit and it will show 4V/17.2Ω="0.232558A" or approximately 0.233A
To find the readings of ammeter A1, let's find the voltage at R56. U56=I2*R56=I2*1
Current I1=U56/2=I2/2=0.116279A or approximately 0.116 A
The voltmeter reading is equal to the difference in voltage drop across resistances R2 and R4. To find these values, let's find the voltage drop across the entire chain of resistances R1R2R3R4. U1234=I2*R1234=I2*7.2
Voltage drop across R2 U2=U1234/(R1+R2)*R2=I2*7.2*12/18=I2*7.2*2/3
Voltage drop across R4 U4=U1234/(R3+R4)*R4=I2*7.2*8/12=I2*7.2*2/3
The voltage difference across R2 and R4 is equal to U2-U4=I2*7.2*2/3-I2*7.2*2/3=0, therefore, the voltmeter readings will be zero.
Answer: ammeter A2 will show a current of approximately 0.233A, ammeter A1 will show approximately 0.116A, and the voltmeter will show 0
I welcome all readers to our website and today, as part of the “ Electronics for Beginners ” course, we will study the basic methods of measuring current, voltage and other parameters of electrical circuits. Naturally, basic measuring instruments such as voltmeter , ammeter , etc. will not be left without attention.
Current measurement.
And we'll start by measuring the current. The device used for these purposes is called an ammeter and it is connected in series to the circuit. Let's look at a small example:
As you can see, here the power supply is connected directly to the resistor. In addition, the circuit contains an ammeter connected in series with a resistor. According to Ohm's law, the current strength in this circuit should be equal to:
We obtained a value equal to 0.12 A, which exactly coincides with the practical result shown by the ammeter in the circuit
