Question

Chỉ cần ý c thôi ạ

Answer 1

c) Ta có mạch (R1//R2)nt(R3//R4)

=>Rtđ=\(\dfrac{R1.R2}{R1+R2}+\dfrac{R3.R4}{R3+R4}=7\Omega\)

=>\(I=\dfrac{U}{Rt\text{đ}}=\dfrac{12}{7}A\)

vì R12ntR34=>I12=I34=I=\(\dfrac{12}{7}A\)

Vì R1//R2=>U1=U2=U12=I12.R12=\(\dfrac{12}{7}.3=\dfrac{36}{7}V\)

=>\(I2=\dfrac{U2}{R2}=\dfrac{36}{7}:6=\dfrac{6}{7}A\)

Vì R3//R4=>U3=U4=U34=I34.R34=\(\dfrac{12}{7}.4=\dfrac{48}{7}A\)

=>\(I4=\dfrac{U4}{R4}=\dfrac{48}{7}:12=\dfrac{4}{7}A\)

Vì I2>I4(\(\dfrac{6}{7}>\dfrac{4}{7}\))=>Chốt dương tại M

Ta có I2=Ia+I4=>Ia=I2-I4=\(\dfrac{2}{7}A\)

Vậy ampe kế chỉ \(\dfrac{2}{7}A\)