179. What is the value of a carbon composition resistor with the following color code: Brown, white, orange, red

Draw a circuit diagram with a three-cell battery in series with an open switch, a resistor, an ammeter showing the current flowing from the resistor, and a fuse. Also, draw a voltmeter measuring the potential difference across the source.

The following three impedances are connected in series across a 40 V, 20 kHz supply: a 
resistance of 8 Ω, a coil of inductance 130 μH and 5 Ω resistance, and a 10 Ω resistor in 
series with a 0.25 µF capacitor. Sketch a neat diagram representing this network, and 
calculate:
5.1.1 The inductive and capacitive reactance’s. (4)
5.1.2 The magnitude and phase angle of the circuit impedance. (4)
5.1.3 The voltage drops across resistance, inductance and capacitance.

Question 1

A simple Zener diode shunt voltage regulator is to supply 12 V to a load which normally draws a load current which varies from 0 to 50 mA. The input voltage varies between 15 V and 18 V.

1.1 Calculate the maximum rated current value of a Zener device to be used.

1.2 Calculate the minimum power for the Zener that could be used safely.

1.3 If a 5 W rated Zener were to be used, calculate the range of possible RS. values and hence suggest a suitable standard E12 resistor value.

1.4 State four (4) conditions under which a Zener diode dissipates minimum power in a regulator circuit.

Question 2 (IEIIQ15)

A 2.5 W Zener diode is used in a simple Zener shunt voltage-regulator to supply 5.1 V to a load which normally draws a load current varying from 0 to 125 mA. The input voltage varies between 8 V and 9.5 V

2.1 Give two (2) reasons for the inclusion of the series resistor in the Zener-regulator circuit.

2.2 Calculate the range of series resistance that may safely be used in this circuit.

2.3 Select a single suitable standard E12 resistor value and give its colour code with 1 % tolerance.