Question

In a circuit L, C and R are connected in series with an alternating voltage source of f. When current in the circuit leads the voltage by 45°, the value of C ____________.

Options

• `1/(2pi"f"(2pi"fL" + "R")`

• `1/(2pi"f"(2pi"fR" + "L")`

• `1/(2pi"f"("R" + "L"))`

• `1/(2pi"f"("R" + 1/"L")`

Answer 1

In a circuit L, C and R are connected in series with an alternating voltage source of f. When current in the circuit leads the voltage by 45°, the value of C `1/(2pi"f"(2pi"fL" + "R")`.

Explanation:

`"tan"  phi = ("X"_"C" - "X"_"L")/"R" Rightarrow "tan"  45° = ((1/(2pi"fC") - 2pi "fL")/"R")`

`therefore "C" = 1/(2pi"f"(2pi"fL" + "R")`