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a. \(R=\dfrac{R1\cdot R2}{R1+R2}=\dfrac{10\cdot15}{10+15}=6\Omega\)
\(U=U1=U2=18V\left(R1\backslash\backslash R2\right)\)
\(\Rightarrow\left\{{}\begin{matrix}I=U:R=18:6=3A\\I1=U1:R1=18:10=1,8A\\I2=U2:R2=18:15=1,2A\end{matrix}\right.\)
b. \(\left\{{}\begin{matrix}P=UI=18.3=54W\\A=UIt=18.3.20.60=64800\left(J\right)\end{matrix}\right.\)
c. \(R1=p1\dfrac{l1}{S1}\Rightarrow l1=\dfrac{R1\cdot S1}{p1}=\dfrac{10\cdot0,1\cdot10^{-6}}{0,4.10^{-6}}=2,5\left(m\right)\)
\(S1=0,1mm^2=0,1.10^{-6}m^2\left(gt\right)\)
\(R_{tđ}=\dfrac{R_1.R_2}{R_1+R_2}=\dfrac{40.60}{40+60}=24\left(\Omega\right)\)
\(U=U_1=U_2=36V\)
\(\left\{{}\begin{matrix}I=\dfrac{U}{R_{tđ}}=\dfrac{36}{24}=\dfrac{3}{2}\left(A\right)\\I_1=\dfrac{U_1}{R_1}=\dfrac{36}{40}=\dfrac{9}{10}\left(A\right)\\I_2=\dfrac{U_2}{R_2}=\dfrac{36}{60}=\dfrac{3}{5}\left(A\right)\end{matrix}\right.\)
\(P=U.I=\dfrac{3}{2}.36=54\left(W\right)\)
\(a,R_{tđ}=\dfrac{R_1.R_2}{R_1+R_2}=\dfrac{60.40}{60+40}=24\left(\Omega\right)\)
\(I_m=\dfrac{U}{R_{tđ}}=\dfrac{12}{24}=0,5\left(\Omega\right)\)
\(b,P_1=\dfrac{U}{R_1}=\dfrac{12^2}{60}=2,4\left(W\right)\)
\(P_2=\dfrac{U^2}{R}=\dfrac{12^2}{40}=3,6\left(W\right)\)
\(P_m=U.I=12.0,5=6\left(W\right)\)
a. \(R=\dfrac{R1\cdot R2}{R1+R2}=\dfrac{30\cdot20}{30+20}=12\Omega\)
b. \(U=U1=U2=IR=2\cdot12=24V\left(R1//R2\right)\)
\(\Rightarrow\left\{{}\begin{matrix}I1=U1:R1=24:30=0,8A\\I2=U2:R2=24:20=1,2A\end{matrix}\right.\)
c. \(R=p\dfrac{l}{S}\Rightarrow S=\dfrac{p\cdot l}{R}=\dfrac{0,5\cdot10^{-6} \cdot2}{30}=3,\left(3\right)\cdot10^{-8}\Omega m\)
a. NỐI TIẾP:
\(\left[{}\begin{matrix}R=R1+R2=40+60=100\Omega\\I=I1=I2=U:R=36:100=0,36A\left(R1ntR2\right)\\P=UI=36\cdot0,36=12,96W\end{matrix}\right.\)
b. SONG SONG:
\(\left[{}\begin{matrix}R=\dfrac{R1\cdot R2}{R1+R2}=\dfrac{40\cdot60}{40+60}=24\Omega\\U=U1=U2=36V\left(R1//R2\right)\Rightarrow\left\{{}\begin{matrix}I1=U1:R1=36:40=0,9A\\I2=U2:R2=36:60=0,6A\\I=U:R=36:24=1,5A\end{matrix}\right.\\P=UI=36\cdot1,5=54W\end{matrix}\right.\)
c. \(\left\{{}\begin{matrix}Q_{toa1}=I1^2\cdot R1\cdot t=0,36^2\cdot40\cdot4\cdot3600=74649,6\left(J\right)\\Q_{toa2}=I2^2\cdot R2\cdot t=0,36^2\cdot60\cdot4\cdot3600=111974,4\left(J\right)\end{matrix}\right.\)
Điện trở của đèn 1: \(P_1=\dfrac{U_1^2}{R_1}\Rightarrow R_1=\dfrac{U_1^2}{P_1}=\dfrac{110^2}{25}=484\left(\Omega\right)\)
Điện trở của đèn 2: \(P_2=\dfrac{U_2^2}{R_2}\Rightarrow R_2=\dfrac{U_2^2}{P_2}=\dfrac{110^2}{100}=121\left(\Omega\right)\)
Do mắc song song nên \(U=U_1=U_2=110V\)
\(\left\{{}\begin{matrix}I_1=\dfrac{U_1}{R_1}=\dfrac{110}{484}=\dfrac{5}{22}\left(A\right)\\I_2=\dfrac{U_2}{R_2}=\dfrac{110}{121}=\dfrac{10}{11}\left(A\right)\end{matrix}\right.\)
Do mắc song song nên \(I_m=I_1+I_2=\dfrac{5}{22}+\dfrac{10}{11}=\dfrac{25}{22}\left(A\right)\)
Công suất của cả đoạn mạch: \(P_m=U_m.I_m=\dfrac{25}{22}.110=125\left(W\right)\)
Điện năng mạch tiêu thụ trong 2h:
\(A=A_1+A_2=P_1.t+P_2.t=2.60.60\left(25+100\right)=900000\left(J\right)=0,25\left(kWh\right)\)
Tiền điện phải trả: \(0,25.1600=400\left(đ\right)\)
\(MCD:R1//R2\)
\(=>R=\dfrac{R1\cdot R2}{R1+R2}=\dfrac{40\cdot60}{40+60}=24\Omega\)
\(U=U1=U2=60V=>\left\{{}\begin{matrix}I1=\dfrac{U1}{R1}=\dfrac{60}{40}=1,5A\\I2=\dfrac{U2}{R2}=\dfrac{60}{60}=1A\\I=\dfrac{U}{R}=\dfrac{60}{24}=2,5A\end{matrix}\right.\)
\(=>Q_{toa}=A=UIt=60\cdot2,5\cdot10\cdot60=90000\left(J\right)\)
a,\(=>Im=I1+I2=5A\)
b,\(R1//R2=>U1=U2=180V=>R1=\dfrac{U1}{I1}=\dfrac{180}{3}=60\left(om\right)\)
\(=>R2=\dfrac{U2}{I2}=\dfrac{180}{2}=90\left(om\right)\)
c,\(=>Im=\dfrac{P}{U}=\dfrac{945}{180}=5,25A=I1+I'\)
\(=>Rtd=\dfrac{R1R'}{R1+R'}=\dfrac{180}{5,25}=>\dfrac{60R'}{60+R'}=\dfrac{240}{7}=>R'=80\left(om\right)\)
\(=>R''=90-80=10\left(om\right)\)
vậy......
a) vì R1//R2 nên Rm=(R1.R2)/(R1+R2)=(60.120)/(60+120)= 40(Ω)
theo đl ôm I=U/R => U=RI=40.1.8=72(A)
công suất tiêu thụ P=UI=72.1,8=129.6(W)
b) vì R1//R2 nên I1/I2=R2/R1=> I1/R2 = I2/R1 = (I1+I2)/(R1+R2) = Im/Rm = 1.8/40=0,045
=> I1= R2.0,045=120.0,045= 5,4 (A)
I2= R1.0,045=60.0,045 = 2,7 (A)
Chúc ht
Rhinder 2k5
a. \(U=IR=1,8\cdot\left(60+120\right)=324V\)
\(\rightarrow P=UI=324\cdot1,8=583,2\)W
b. \(U=U1=U2=324V\left(R1//R2\right)\)
\(\Rightarrow\left\{{}\begin{matrix}I1=U1:R1=324:60=5,4A\\I2=U2:R2=324:120=2,7A\end{matrix}\right.\)