chapter two ohmmeter

Question 1

diff ohmmeter

Answer 1

it is an electric circuit by which we can determine the value of unkown resistance directly

Question 2

what is the relation on the ohmmeter

Answer 2

at short circuit

R_ohmmeter = V_B\I_g

R_ohmeter = R_g + R_c + r + R_v + …….

BY coonctein a resistor [R_x]

R_ohmeter + R_x = V_B\I

Question 3

what is the scintefic idea for operation ohmmeter

Answer 3

it depends on ohmss law for closed circuit ( I = V_B \ R_t )

there for ( I & 1 \ R_t )

adding an extranl resistance between the terminals of the circuit of the ohmmeter causes drop in the flowing current then the resistance can be calcluted using ohms law for closed circuit ( R_t = V_B \ I )

Question 4

what is the construction of the ohmmeter

Answer 4

draw in the page 102

1. I_g ; 400 mili amp , R_g ; 250 ohm [microammeter]
2. fixed resistor of 3000 ohm
3. variable resistor of range [0 ; 6565] ohm
4. 1.5 volt dry cell

Question 5

ohmmeter scale runs backward ( in reverse direction to that if the micrometer) GR

Answer 5

because I&1\A

zero extrernal resistance produces full scale deflection and the larger the unknown resistance , the smaller the deflection

Question 6

ohmeter scale is not uniform GR

Answer 6

I = VB \ Rg + Rc + Rv + r + Rx

because the current intensity i is inversely proportioonal to the total resistance in the circuit , not with unknown resistance only

Question 7

using rheostat in the ohmeter GR

Answer 7

to adjusit the current intensity through the circuit of the ohmeter so its pointer will be adjusted at the end of its scale [0 ohm] when it is short circuited

Question 8

using the fixed resistor in the ohmmeter GR

Answer 8

to decrease the electric current intensity through the cinstrument so i will protect the ohmmeter from damage

Question 9

using battery of fixed E.M.F in the ohmmeter GR

Answer 9

I = VB \ Rg + Rc + Rv + r + Rx

to be sure that drop that taked place in the current depends only on the external resistance

Question 10

diff

digital muli meteres

DC muli meter

AC muli meter

Answer 10

1. they are insturment produce its reading of the measured voltage current and resistance on small [LCD] [liquid crystal display] without a pointer
2. they are instrument measure the direct voltage or current
3. they are instrument measure the alternating voltage or current