Three equal charges, each having a magnitude of 2.0 x 10-6 C, are placed at the three corners of a right angled triangle of sides 3 cm, 4 cm and 5 cm. The force (in magnitude) on the charge at the right angled corner is
50 N
26 N
29 N
45.9 N
D.
45.9 N
Consider the diagram
q
qA = qB = qC = 2 × 10-6 C
The sides of right angle triangle
AB = 3 cm
BC = 4 cm
AC = 5 cm
The force on A due to B is
FA =
= 9 × 109 ×
FA = 40 N ( along BA)
The force on B due to C is
FC =
=
FC = 22.5 N ( along BC )
The resultant force on the charge at B,
F =
=
F = 45.9 N
The parts of two concentric circular arcs joined by two radial lines and carries current i. The arcs subtend an angle 0 at the centre of the circle. The magnetic field at the centre O, is
The ammeter shown in figure consists of a 480 Ω coil connected in parallel to a 20 Ω shunt. The reading of ammeter is
0.125 A
1.67 A
0.13 A
0.67 A
An inductor (L = 20 H), a resistor (R = 100 Ω) and a battery (E = 10 V) are connected in series. After a long time, the circuit is short-circuited and then the battery is disconnected. Find the current in the circuit at 1 ms after short circuiting.
4.5 x 105 A
3.2x 10-5 A
9.8 × 10-5 A
6.7 × 10-4 A
Two charges of + 10 μC and +20 μC are separated by a distance 2 cm. The net potential (electric) due to the pair at the middle point of the line joining the two changes, is
27 MV
18 MV
20 MV
23 MV
A copper rod of length 20 cm and cross-sectional area 2 mm is joined with a similar aluminium rod as shown below
The resistance of pair of rods is (ρAl =2.6 x 10-8 Ω-m and ρCu =1.7 x 10-8 Ω-m)
1.0 mΩ
2.0 mΩ
3.0 mΩ
None of these
A square loop is made by a uniform conductor wire as shown in figure
The net magnetic field at the centre of the loop if side length of the square is a
zero
None of these
The electron of H - atom is revolving around the nucleus in circular orbit having radius with . The current produced due to the motion of electron is
zero
Two small balls, each carrying a charge q are suspended by equal insulator strings of length l m from the hook of a stand. This arrangement is carried in a satellite in space. The tension in each string will be