Physics

Suva Grammar School

Department of Mathematics / Physics

Form 7 Physics Assignment 1, Term 2 – 2004

1. A satellite is orbiting the earth in a circular orbit. Use Newton’s laws to derive the expressions for velocity ( v ) and period ( T ) of motion of the satellite in terms of M and r. (2)

2. In a nichrome wire, electrons move with a drift velocity of 0.08 mm/s through a cross-sectional area of 7 mm2. There are 1028 electrons in each m3 of wire.

Calculate the size of the current.

Determine the current density in the wire.

( electronic charge, e = 1.602 10-19 C ) (3)

3. A galvanometer reads 1 mA at full-scale deflection (fsd) and has an internal resistance of 120 (. This is to be converted to an ammeter to read up to 6 A at full – scale.

Draw a circuit diagram to show the conversion.

Calculate the value of the resistance needed for this conversion. (3)

4. A galvanometer reads 5 mA at full-scale deflection (fsd) and has an internal resistance of 90 (. This is to be converted to a voltmeter to read up to 10 V at full – scale.

Draw a circuit diagram to show the conversion.

Calculate the value of the resistance needed for this conversion. (3)

9 V

5. In the multi-loop circuit shown, find:

the current in R. E 2.5 A

the value of R.

the unknown emf (E).

1.5 A

(3)

6. A copper wire of length 3 m and circular cross-section, of radius, r = 1.2 mm. The resistivity of the given wire is 1.7 10-8 (m.

Calculate the resistance of the wire.

What current will flow if a potential difference of 12 V is applied? (3)

7. The circuit below shows a multi – loop circuit.

a 12 V 6 ( b

I1

4 ( 8 V

d c

I3

I2

3 (

e f

Using Kirchoff’s laws;

Write an equation relating the currents.

Write voltage equations for the loops:

(I) abcda (II) dcfed

Calculate the values of the...