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1999 WAEC Physics Theory (a) Sketch the magnetic flux pattern around a long; straight, current-carrying wire (b) State two...

Physics
WAEC 1999

(a) Sketch the magnetic flux pattern around a long; straight, current-carrying wire

(b) State two methods by which the sensitivity of a moving-coil galvanometer can be increased.

(c) A series RLC circuit comprises a 100-\(\Omega\) resistor, a 3-H inductor and a 4-\(\mu\)f capacitor. The a.c source of tile circuit has an e.m.f of 100V and a frequency of 160 Hz.

(i) Draw the circuit diagram of the arrangement. Calculate the:

(ii) capacitive reactance;

(iii) inductive reactance:

(iv) impedance of the circuit;

(v) current in the circuit;

(vi) average power dissipated in the circuit.

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Explanation

(a)


(b) The sensitivity is increased by a weak spring and increasing the strength of the magnet C
(c)(i)


(ii) X = \(\frac{1}{2 \pi FC} = \frac{1}{2 \pi \frac{160}{\pi} \times 4}\) = 781\(\Omega\)

(iii) X\(_L\) = 2\(\pi\)fL = 2\(pi\) x \(\frac{160}{\pi}\) x 3 = 960\(\Omega\) 

(iv) Z = \(\sqrt{R^2 + (X_L - X_c)^2} = \sqrt{100^2 + (960 - 781)^2}\) = 205\(\Omega\) 

(v) I = \(\frac{v}{z} = \frac{100}{205} = 0.49A\)

(vi) P = I\(^2R\) = (0.49)\(^{2}\) x 100

= 23.795 W = 24W


 

 


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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995