Two resistors, R1 and R2, with resistance values of 5 and 10 ohm respectively, are connected in parallel to a 15 V power supply,

Two resistors, R1 and R2, with resistance values of 5 and 10 ohm respectively, are connected in parallel to a 15 V power supply,

1、 The voltage at both ends of each branch in parallel circuit is equal to the total voltage at both ends of parallel circuit: u = 15V
2、 The currents in each branch are as follows:
I1=U/R1=15V/5Ω=3A,
I2=U/R2=15V/10Ω=1.5A.
3、 The main current is:
I=I1+I2=3A+1.5A=4.5A.
4、 The total resistance of parallel circuit is r = u / I = 15V / 4.5a = 3.33 Ω
5、 The power of each branch is as follows:
P1=UI1=15V×3A=45W,
P2=UI2=15V×1.5A=22.5W.
6、 The total power of the parallel circuit is:
P=P1+P2=45W+22.5W=67.5W

Resistance R1 = 4 Ω, R2 = 6 Ω, connected in parallel at both ends of 6V power supply, at this time, the total resistance of the circuit through R1 current, R2 voltage
I'm sorry, I copied it. The last question is what is the total current?

Total resistance = 6 × 4 / (6 + 4) = 2.4 Ω
Current through R1 = 6V / 4 Ω = 1.5A
Current through R2 = 6V / 6 Ω = 1A
Total current = 6V / 2.4 Ω = 2.5A or 1.5 + 1 = 2.5A

Connect R1 = 10 ohm resistor and R2 = 20 ohm resistor in series to 12 power supplies
What is the current in this circuit? What is the voltage at both ends of R1? What is the voltage at both ends of R2?

From I = u / R,
I = u / R total = 12V / (10 Ω + 20 Ω) = 0.4A
Because the current of series circuit is equal everywhere, the voltage at both ends of R1 is V1 = I * R1 = 0.4A * 10 Ω = 4V
R2 two terminal voltage V2 = I * R2 = 0.4 * 20 Ω = 8V
I hope my answer will help you

Use resistor R1 = 10 ohm and R2 = 20 ohm in series, which means their total resistance is（
A is less than 10 Ω B is between 10-20 Ω C is more than 20 Ω D cannot be judged

C. The series resistance is equal to the sum of them, R1 + R2 = 30 Ω