The voltage across a load is v(t) = 60(ωt-10)cos V and the curre...
The r.m.s. values of voltage and current phasors are :
Vr.m.s.=60/√2∠-10∘V;
Ir.m.s.=1.5√2∠-50∘
∴ Complex power,
S = Vr.m.s.I*r.m.s.
=60√2∠-10∘×1.5/√2∠-50∘
Complex power,
S=45∠-60∘VA-(22.5-j38.97)VA.
Therefore, reactive power = 38.97 VAR, leading because reactive power is negative.
View all questions of this test
The voltage across a load is v(t) = 60(ωt-10)cos V and the curre...
1 - e^(-t/RC)) volts, where t is time in seconds, R is the resistance in ohms, and C is the capacitance in farads.
To find the time constant of the circuit, we can use the formula:
τ = RC
where τ is the time constant in seconds.
Since the voltage equation is given as v(t) = 60(1 - e^(-t/RC)), we can rearrange it to solve for τ:
v(t) = 60(1 - e^(-t/RC))
v(t)/60 = 1 - e^(-t/RC)
e^(-t/RC) = 1 - v(t)/60
Taking the natural logarithm of both sides:
-ln(1 - v(t)/60) = t/RC
Multiplying both sides by RC:
t = -RC ln(1 - v(t)/60)
Now we can plug in values for v(t) and solve for τ:
v(t) = 60(1 - e^(-t/RC))
When t = τ, e^(-t/RC) = 1/e, so:
v(τ) = 60(1 - 1/e)
Solving for τ:
τ = RC = t/(-ln(1 - v(τ)/60))
τ = t/(-ln(1 - 60(1 - 1/e)/60))
τ ≈ 0.693 RC
Therefore, the time constant of the circuit is approximately 0.693 times the product of the resistance and capacitance.