# Determine the required value of the shunt resistance if the maximum value of the current I is 200 A. The meter can read a maximum of 1 mA and has a resistance of 0.1 Ω.

**MODULE TITLE : ENGINEERING SCIENCE TOPIC TITLE : D.C. CIRCUITS**

**Determine the required value of the shunt resistance if the maximum value of the current I is 200 A. The meter can read a maximum of 1 mA and has a resistance of 0.1 Ω.**

(b) If the shunt is made of copper and has a cross-sectional area of 25 cm2 calculate its required length.

**2. The circuit of FIGURE 2 shows a 10 kΩ potentiometer with a 5 kΩ load. Determine the position of the slider on the ‘pot’ when the voltage across points ‘XX` is 3 V. **

3. (a) Calculate the value of the current through the 12 V battery shown in FIGURE 3.

(b) Calculate the power dissipated in R1, R2 and R.

If the magnetic flux linking all the turns of a 50 turn coil changes from 10 mWb to 20 mWb and induces an e.m.f. of 62.5 V in the coil, calculate the time over which the flux changes.

**5. A 500 mm conductor inside an electric motor has a force of 1.5 newtons exerted on it. If it is at right angles to a magnetic field of flux density 0.6 T, calculate the current flowing in the conductor. **

**6. FIGURE 4 show the construction of a multi-plate variable capacitor having 4 pairs of plates. The plates, when closed, are separated in air by 0.01 mm and a capacitance range of 10 to 400 pF is required.**

(a) Estimate the required radius, R, of each plate

(b) The capacitor is set to the maximum 400 pF and is charged to 10 V through a 50 kΩ resistor. Determine:

(i) the initial value of current flowing.

(ii) the time constant for the circuit.

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