Kirchhoff's first law i.e. $\Sigma i=0$ at a junction is based on the law of conservation of :

(1) Charge

(2) Energy

(3) Momentum

(4) Angular momentum

The figure below shows currents in a part of electric circuit. The current i is

(1) 1.7 amp

(2) 3.7 amp

(3) 1.3 amp

(4) 1 amp

The figure shows a network of currents. The magnitude of currents is shown here. The current i will be 

(1) 3 A

(2) 13 A

(3) 23 A

(4) – 3 A

The current in the arm \(CD\) of the circuit will be:
             
1. $i_1+i_2$

2. $i_2+i_3$

3. $i_1+i_3$

4. $i_1-i_2+i_3$

Kirchhoff’s first and second laws for electrical circuits are consequences of: